We described two new species collected from Miscanthus spp. in Thailand and Taiwan. One of the new species, Stigmaeopsis inthanonsis Saito, Kongchuensin & Sahara n. sp., was found in Thailand (Inthanon National Park). The other species from Taiwan, named Stigmaeopsis formosa Saito, Chao & Sato n. sp. was previously referred to as T-form or ML form of Stigmaeopsis miscanthi (Saito). Thus 15 species are now involved in the genus Stigmaeopsis. Because five species inhabiting Miscanthus grasses are resemble together, we call them as Stigmaeopsis miscanthi species group. An updated key to all known species of Stigmaeopsis is proposed.