Hong Kong's Commercial Radio quoted Tan's lawyer Pu Zhiqiang as saying the Chengdu Intermediate People's Court convicted Tan of publishing articles about the Tiananmen Square massacre, but made no mention of the quake or building collapses that killed some 88,000 people, including thousands of students.
Tan intends to appeal the sentence, the lawyer said.
The court barred Tan's family from entering the court for the ruling, while nine Hong Kong reporters who gathered outside the court for the case were manhandled by police.
Tan, 55, was detained by Chengdu police in March last year and indicted for allegedly "inciting subversion of state power" in August.