The official Xinhua news agency said on Sunday that the man, identified as a 32-year-old with the surname Lao, had died in Guangdong province.
Lao, who was the 15th human bird flu case in China, had symptoms of fever and pneumonia on 22 February and died on 2 March, Xinhua said.
The symptoms appeared after he made several visits to an agricultural market where he spent a long time near "a live poultry slaughtering site", it added.
Of the 14 previous cases in China, eight were fatal, two are under treatment and the other four have recovered.
China has reported more than 30 outbreaks of the H5N1 strain in birds across the country in the past year.
None of these has been in Guangdong, but neighbouring Hong Kong has confirmed several cases, fuelling suspicions that the authorities are not being truthful about the situation in Guangdong province.
A Hong Kong government spokesman said it would suspend imports of all live poultry from Guangdong for three weeks starting from Monday.
Day-old chicks and pet birds would also be barred from import, he added.
In Europe, France announced a new case of H5N1 in a wild duck in the east of the country, while another test on a wild swan showed the virus had spread several hundred kilometres to the south.
France's poultry sector, Europe's biggest, is losing $48 million a month after an outbreak of H5N1 at a poultry farm.
The news prompted more than 40 countries to impose curbs on French poultry products.
"There is no way to put a big cage around the United States. I think it is fair to assume we'll deal with ... avian influenza"
US Agriculture Secretary
In eastern Europe, Poland detected its first case of bird flu in two swans found dead.
Mike Johanns, the US Agriculture Secretary, said on Saturday the United States was preparing for an outbreak of avian flu but assured consumers that poultry remained safe to eat.
"There is no way to put a big cage around the United States. I think it is fair to assume we'll deal with ... avian influenza," said Johanns.
"We could see it in domestic flocks as well as [wild] birds."
The bird flu virus made its first known jump to humans in Hong Kong in 1997, killing 6 people.
The virus has infected birds in at least 14 new countries over the past month, spreading across Europe and reaching Egypt and West Africa, fuelling fears for the poultry industry and human health.