Du Daobin, 40, had written and posted 28 articles on the internet which "incited subversion of state power and overthrow of China's socialist system", a spokesman for the Public Security Bureau in the central province of Hubei said.
Du, who has been detained since October, also accepted money from overseas organisations and individuals in return for helping them post articles harmful to state security on domestic websites, official news agency Xinhua quoted the spokesman as saying.
Subversion of state
Du had overstepped his legal right to criticise government work and civil servants with good intent, and viciously incited subversion of state power through fabrication, Xinhua said.
Du, who worked in the medical insurance office of Yingcheng city in Hubei province before his detention, had confessed to most of his crimes and a judicial inquiry had been opened, it said.
Police could not immediately be reached for comment.
Du's case has drawn protests from scores of Chinese academics and reporters who have urged his release. Activists have written to Premier Wen Jiabao saying Du's detention was
Support for Du
Internet surfers have flocked to Du's defence, even posting an online petition at www.mzyzy.com saying he had not called for the overthrow of the Chinese government.
Du's detention was a misuse of the subversion law to stop free speech, the petition said.
China has stepped up a crackdown on internet content from politics to pornography, struggling to gain control over the medium. Authorities have created a special internet police force, blocked some foreign news sites and shut down domestic sites posting what they consider politically incorrect literature.