Yan Jun, 32, was found guilty of "inciting subversion" by the Xian Intermediate People's Court, his mother Dai Yuzhen said on Moday.
"The court took no more 20 minutes," Dai said by telephone from Xian in Shaanxi province.
Family members and Yan could not understand the court's decision, Dai said.
"I can't accept this verdict. Just because he wrote a few essays, he's going to jail. I can't make sense of it," Dai said.
The sentencing came as Chinese Premier Wen Jiabao arrived in the United States on an official visit.
The Hong Kong-based Information Centre for Human Rights and Democracy called on Washington to press Wen to improve China's human rights record.
"I can't accept this verdict. Just because he wrote a few essays, he's going to jail. I can't make sense of it"
Yan Jun's mother
"We call on Bush to pressure Wen Jiabao to open up the internet, allow religious freedom and allow workers to set up independent unions," the Centre's director, Frank Lu said in a statement.
Yan came into the spotlight in 1998, when he was arrested along with three others in Xian when former US president Bill Clinton visted the city. The four were released two days later.
The leading dissident was arrested in April after posting five articles on the internet. One essay called for a reassessment of the 1989 crackdown on student demonstrators on Tiananmen Square.
Another asked the government to free former communist party general secretary, Zhao Ziyang, who was deposed and placed under house arrest after he showed sympathy towards the students in 1989.
Yan's other essays called for freedom of the press and of expression and for the government to allow workers to set up independent unions.