Wu Gan, a blogger better known by his online name "Super Vulgar Butcher", regularly championed sensitive cases of government abuses of power, both online and in street protests. He was detained in May 2015 and later charged with subversion.
Yan Xin, Wu's lawyer, told Reuters he planned to appeal against the eight-year sentence handed down by the Tianjin Municipality's No. 2 Intermediate People's Court.
Wu criticised China's political system online and used performance art to create disturbances, as well as insulting people and spreading false information, according to a statement form the court posted on its website.
"He carried out a string of criminal actions to subvert state power and overthrow the socialist system and seriously harmed state security and social stability," the court said.
Wu had been using his platform before his arrest to cast doubt on the official version of events in a controversial case in which a police officer shot a petitioner in a train station in northern China's Heilongjiang province in May 2015.
His sentence is the most severe yet in what rights groups have called an unprecedented attack on China's rights activists and lawyers, known as the 709 crackdown, which began in earnest on July 9, 2015.
The hardline approach to rights activism has shown no sign of softening as Chinese President Xi Jinping enters his second five-year term in office.
The decision to release the sentence the day after Christmas, when there would likely be less attention from diplomats and international observers, "reeks of cynical political calculation", said Patrick Poon, Hong Kong-based researcher for Amnesty International.
China's foreign ministry could not respond immediately to a request for comment.
Wu's detention led to his father, Xu Xiaoshun, also taking up activism. Xu told Reuters in July he felt compelled to speak out on his son's behalf after authorities asked him to say Wu was guilty.
The crackdown has also spurred other family members to take up activism.
(Reporting by Christian Shepherd; Editing by Paul Tait)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)