Do I need to submit separate visa applications to travel to reunion island and Martinique?

Don't. French overseas departments and territories include the following areas: reunion island, French Polynesia (Tahiti), GuaTrop, Guyana, Martinique and Mayotte. China citizens only need to apply for a visa once to go abroad, and there is no need to submit another visa application to reunion island and Martinique. Visa is a kind of license issued by a government agency for foreigners applying for entry, exit or transit according to the provisions of domestic laws.