Human rights lawyer Pu Zhiqiang could be charged with "collusion" with foreign powers, and get ten years in prison.
Chinese police questioned the dissident about meetings with a former US ambassador to China, his frequent trips to Japan, and his online "insults" against senior officials, including Mao's grandson.
Pu's lawyer Zhang Sishi said that in February Pu met Ambassador Locke who had asked him to share his views on human rights.
Beijing police questioned Pu about his frequent trips to Japan, asking him "why he traveled to Japan four times every year", Zhang said. The reason is that Pu's son studies in Japan.