Lawyers for a group of 40 Chinese victims made the announcement at a press conference in Tokyo on Wednesday.
They said the victims in China's northeastern city of Qiqihaer would demand Japan compensate for medical care and life support for the injuries sustained from a toxic gas leak, from chemical weapons abandoned in China by the Imperial Japanese Army.
If they see the Japanese government is not addressing their plight adequately after the petition is filed on August 4, the group will bring a lawsuit seeking an apology and damages.
August 4 marks the second anniversary of the incident in which barrels of deadly chemical weapons were discovered at a construction site with one accidentally broken, killing one local resident and injuring 43 others in Qiqihar City.
Japan has paid China 300 million yen in the name of "costs for the disposal of chemical weapons abandoned" in the city after World War II.