Abstract: This paper deals with a new species of Eusimulium from Yadong, Tibet, China. The female, pupa and larva of Simulium(Eusimulium)novigracilis sp. Nov. are described.The new species belongs to the latipes-group. By the shape of cocoon and the number of filaments, this new specis is similar to S (E.) gracilis Datta, 1973 (from India) and S(E.) bertrandi Grenier & Defter, 1959(from France), but is distinguished from them by: theshape of cibarium base (fig. 3), the third segment of maxillary palp (fig2)with median large sensory vesicle opening at the end, in female; the shape of terminalia of male and female; head and thoracic trichomes single, the arrangement of filaments(fig. 8), the shape and the lenth of the mid-dorsal projection of pupa; the shape of postgenal cleft (door-arched shape) and the shape of anal sclerite of larva.