The genus Colocasiomyia de Meijere (Diptera, Drosophilidae) is known to include 30 described and nearly 60 undescribed species classified into six species groups. Among these, the C. gigantea group of seven known species (two Southeast Asian and five Chinese) proved to be peculiar for its specificity on monsteroid (subfamily Monsteroideae, family Araceae) host plants. In this paper, two new species, C. todai Jiao & Gao, sp. nov. and C. liae Jiao & Gao, sp. nov., are described as members of the C. gigantea group with specimens collected from inflorescences of the monsteroid host species Rhaphidophora peepla (Roxb.) Schott and R. crassicaulis Engl. & Krause, respectively, in Yunnan, China. The two new species are delimitated, in comparison with all known species, based on not only morphological but also DNA barcode (partial sequence of the mitochondrial COI, i.e., cytochrome c oxydase subunit I, gene) data. A revised key to all the nine species of the C. gigantea species group is provided.