Wang Quanzhang was taken into custody in July 2015, one of more than 200 lawyers and activists detained as part of a mass crackdown on human rights defenders across China.
Wang, known for his advocacy of practitioners of the banned Falun Gong spiritual movement and Christians, is the last lawyer still behind bars as part of the sweep.
As the trial was taking place, protesters, some of whom had traveled from other cities, gathered outside the court in Tianjin.
Many were quickly bundled into police cars and taken away amid a heavy security presence surrounding the court.
China regularly sends high-profile detainees and dissidents to court around the Christmas period, taking advantage of the large absence of the international media and diplomatic community.
Human rights activist Wu Gan was sentenced to eight years in prison on Christmas Day in 2017, while Nobel Laureate Liu Xiaobo was imprisoned on the same day in 2009.
Doriane Lau, China researcher with Amnesty International, said in a statement Wang's trial was a "cruel charade" and called for him to be released "immediately."
"This is a sham trial in which Wang Quanzhang is being persecuted only for peacefully defending human rights," Lau said. Lau said there was a "grave risk" Wang had been tortured and mistreated in detention.
Wang's trial began on Wednesday morning local time, and is being held behind closed doors due to the nature of the charges. It isn't clear how long the trial will last or when the final sentence will be handed down.
Wang's wife, Li Wenzu, has been campaigning relentlessly for his release ever since her husband's detention. In April she marched from Beijing to Tianjin on foot to "find her husband."
She was one of four spouses of high-profile human rights lawyers who protested against their detention in front of the Supreme People's Court on December 17, publicly shaving their heads in protest as the word "hairlessness" sounds similar to "lawlessness" in Chinese.
Due to the tight control of China's authoritarian government and harsh penalties for protesting, public demonstrations in China over politically sensitive topics are rare.
After security guards stopped her from presenting a letter petitioning for her husband, Li said judges had behaved in a "lawless" manner around Wang's trial.
"It has been almost two years since the case of Wang Quanzhang was filed to the court, but the judges in charge of this case have been avoiding meeting us, and our lawyer is not allowed to see the court paper," she said at the protest.
"This case has been endlessly delayed ... so I came here today to ask the Supreme Court to fulfill its responsibility of supervising and to correct the subordinate court's unlawful behaviors."
Li was also visited by German Chancellor Angela Merkel during her last visit to China in May.