Foreign Ministry Spokesman Qin Gang said China lodged solemn representation to Japan asking it to immediately stop the action by Japanese politicians as it seeks to undermine China's territorial sovereignty.
Any unilateral action taken by Japan with regards to the island chain is illegal and invalid, Qin said, according to the news agency.
China's protest comes a day after Japan deported 14 Chinese nationals who were arrested in the area after some of the group landed on the uninhabited islands on Wednesday.
Both countries claim sovereignty over the uninhabited islands, which China calls Diaoyu and Japan calls Senkaku. Ownership of the islands would give either nation exclusive oil, mineral and fishing rights in surrounding waters.
Some Japanese lawmakers and members of right-wing groups plan to go to the Diaoyu Islands waters to mourn war dead today.