Xu Zhiyong is accused of having "gathered crowds to disrupt public order" according to a summons delivered to his home, the South China Morning Post reported Wednesday.
Attorney Wang Weiguo said Xu was taken to the No. 3 Detention Center in Beijing.
Xu, a law lecturer at Beijing University of Posts and Telecommunications, is the most prominent representative of the Gongmeng citizen movement.
He has been calling for government transparency and respect for individual rights guaranteed by the Chinese constitution.
Personal friend Teng Biao said the arrest was probably in the planning for some time.
"They arrested people around him to prepare for his arrest," Teng said.
Last month the Supreme People's Protectorate issued a notice calling on prosecutors to crack down on illegal gatherings "with the objective of subverting state power."