Liu Shaoming, a former factory worker, was detained in southern Guangdong province in May 2015 after describing his involvement in the pro-democracy movement on a US website.
Liu's lawyer, Wu Kuiming, told AFP the verdict was announced by the Guangzhou Intermediate People's Court.
"His crime is 'inciting subversion of state power,'" Wu said. "The evidence is some online articles he wrote to recall the June 4 event."
Wu said they will appeal the court decision.
Several Chinese rights advocates have been jailed for trying to keep alive the memory of the Tiananmen Square pro-democracy movement that was crushed by the military.
Liu, who was featured earlier this year in the documentary "We the Workers," travelled to Beijing to join the student-led demonstrations.
According to Amnesty International, he was also a member of China's first independent trade union.
"This is a most callous and unjust verdict against Liu Shaoming," William Nee, China researcher at Amnesty International, said in a statement.
"He is a prisoner of conscience and must be immediately and unconditionally released. All that Liu Shaoming is guilty of is the legitimate exercise of his freedom of expression."