Qin Zhihui among hundreds of bloggers reportedly detained in an official campaign to assert greater control over China's popular social media was found guilty of "slander" and "picking quarrels and provoking troubles", state broadcaster CCTV said.
China has said the rumour crackdown launched last year is aimed at maintaining social order, but rights groups have accused Beijing of limiting freedom of speech online to protect the ruling Communist Party.
Prosecutors at a Beijing district court said Qin had "impacted society and seriously harmed social order" by posting a series of inaccurate reports on Sina Weibo, a Chinese equivalent of Twitter, the official Xinhua news agency said.
It added that the 30-year-old had posted several false reports, including one saying Beijing had granted 200 million yuan ($32.2 million) in compensation to a foreigner who died in a train crash in east China.
Reports said Qin had run a "black PR" firm, taking money from companies to post comments online discrediting rivals. He pleaded guilty and apologised for his crime at a hearing last week, Xinhua said.
Separately, Chinese-American blogger and outspoken government critic Charles Xue was released on bail on Wednesday after being arrested in August for suspected involvement in prostitution and "group licentiousness", a euphemism for group sex.
The 60-year-old Xue had attracted 12 million followers on Weibo, and during his detention was shown making an apology on state television.
Authorities judged he "no longer posed a danger to the public", the state-run Global Times newspaper said on Thursday, adding that the blogger was suffering from an illness.
Chinese microblogs have become drivers of public opinion in recent years, with commenters drawing attention to official corruption, pollution and other issues.
Under regulations announced last September, Chinese Internet users may face three years in prison for writing defamatory messages that are re-posted 500 times.
Web users may also be jailed if offending posts are viewed more than 5,000 times.
Hundreds of bloggers have been arrested since the campaign began, rights group Amnesty International has reported.