Du Daobin, sentenced in 2004 for subversion, would have ended his parole Aug. 4, less than a week before the Aug. 8 start of the games.
A human rights organization said six security officers hustled Du Monday from his job. The local court had no comment.
Police charged Du with posting writings on foreign Web sites and failed to inform authorities about his activities, the Center for Human Rights and Democracy said.
In early July, Amnesty International asked Chinese President Hu Jintao to release political prisoners before the start of the Olympics.
In 2003, Du was sentenced to three years for what Chinese authorities charged was "incitement to subvert state power."
AHN, and more on Reporters Without Borders and Chinese Human Rights Defenders