In this paper, a checklist of four tee n species of Danainae in Taiwan are presented, with keys to all known genera and species. The genital morphology of all species are described in details, the pictures of genitalia are provided. Idea kwashotoensis (Sonan, 192 8) is regarded as a distinct species in this paper, its genitalia is described and the difference between Idea kwashotoens is (Sonan, 1928) and Idea leuconoe clara (Butler, 1867) are discussed.