Blair held eight hours of discussions with Wen over the course of his two-day stay and said he noticed subtle differences from previous visits.
"There was a genuine sense of engagement. I don't want to put that any higher than it deserves but it's there," he said.
"The one thing that I found that was, I would say, different from the very first visit I would have had to China, was that there was no desire to escape this topic [of democracy]."
Blair is seeking to boost Europe's trade links on a two-day visit to China for a European Union-China summit, but said many potential investors have concerns about human rights problems and Beijing's authoritarian government.
Human rights groups have accuse China of suppressing independent religious organisations and harassing labour and political activists.
They also criticise authorities' enforcement of a birth-control policy that limits most urban couples to one child and its use of capital punishment.
China says it has worked hard to ensure basic human rights by reforming its economy, which has improved the overall standard of living of its people.
"It's not that people resent China, but they've got a question mark," Blair said.
"In a country that is developing very fast ... there is unstoppable momentum there towards greater political freedom, progress on human rights"
British Prime Minister Tony Blair
"Will this development economically be matched by political development? ... China has to understand that people see a new China emerging and want to know what kind of country they're dealing with."
He said Wen seemed to grasp such worries.
"I think there is a general understanding of that concern on the Chinese side," Blair said.
He added that he believed China would grow more democratic.
"In a country that is developing very fast ... there is unstoppable momentum there towards greater political freedom, progress on human rights."
Trade and investment
The British leader initially met Wen on Monday at the annual EU-China summit which he attended as part of Britain's turn at the six-month rotating presidency of the 25-nation bloc, and then on Tuesday on the bilateral leg of the trip.
Trade and investment took up most of their time but they also touched on other subjects such as human rights, China's market economy status, Taiwan and Hong Kong, Blair's spokesman said.
"I think it is fair to call our meetings in-depth, practical, frank and productive ones," said Wen.
"I do believe that this is a very important visit and we can exchange views on our bilateral relations and major international and regional issues of common concern."
Blair was in China for the Sino-EU
summit and bilateral talks
Blair praised the approach China had taken over the two days, which included a settlement of a Sino-EU trade row that had left 80 million Chinese-made garments piled up in European ports.
"The length of our meetings both yesterday and today gave us an opportunity to both discuss issues in-depth, but it has really been the frankness and openness of our discussions that has been most appreciated," he told Wen.
He said it had made him "very content indeed".
"I think it has given us an opportunity ... not just to discuss here economic and trade [issues], but also the major political questions in a lot of depth and also with a lot of open discussions that I think has greatly assisted in deepening the understanding between our two countries," said Blair.
Among other issues, the two sides reviewed the programmes of task forces they set up during Blair's last visit in 2003 to ease bilateral trade and investment, finance, energy, education and culture.
Britain is the largest European investor in China, pumping a total of $12 billion into the country by the end of last year.
The Sino-EU trade row on Chinese
garment exports was settled
At a breakfast meeting with Chinese investors on Tuesday, Blair predicted trade and investment between Britain and China could reach $40 billion in the next five years.
"I said to them that the United Kingdom is open for business," said the British prime minister.
Blair oversaw a series of contracts between British or European companies and China, including a deal for China Southern Airlines to buy 10 Airbus A330 jets for $1.5 billion from the European consortium.
Britain's Standard Chartered Bank meanwhile signed an agreement to take a 19.99% stake worth $123 million in Bohai Bank - China's first national joint stock bank since 1996.
Travelling with Blair were about 40 top executives from British and European companies such as Airbus, BP, British American Tobacco, Deutsche Post, GlaxoSmithKline, Rolls Royce and Royal Dutch Shell.
His visit also has a strong cultural element with the likes of prima ballerina Darcy Bussell, football great Sir Bobby Robson, track star Colin Jackson and architect Sir Norman Foster giving "master classes" in Beijing.
A bilateral agreement was penned on cultural exchanges between the two governments.
Later on Tuesday, Blair, along with European Commission President Jose Manuel Barroso and EU foreign policy chief Javier Solana, are to travel to New Delhi, India.