Wang Gongquan, 51, is one of the most prominent Chinese entrepreneurs to push for political reform and is a leading member of an organization campaigning for citizen's rights, the Post reported.
Police escorted Wang from his Beijing home, reported an fellow activist who spoke to Wang's wife.
The summons warrant, which the Post saw, accused Wang of "organizing a mob to disturb public order."
Wang's house was searched for about two hours and his computer seized, said fellow activist and columnist Chen Min, known by his pen name Xiao Shu. Chen and Wang co-authored a petition in July seeking the release of another prominent dissident, Xu Zhiyong.
Wang, Chen and Xu are members of the New Citizens Movement, an organization that advocates civil society, the rule of law and limits to the power of Communist Party officials, the Post said.
Chen said the detention and interrogation of Wang was part of a crackdown on the New Citizens Movement and on opinion leaders who use social media to criticize the government.
"The government is launching a boxing combination to punish people who dare to challenge its authority in the public," Chen said. "It's a very serious warning for everyone. I am prepared for the worst."