Abstract: Protozoan flagellates of the genus Trypanosoma are first found in fish, subsequently found in almost all classes of vertebrates and transmitted from host to host by blood-sucking arthropod or leech vectors. They are harmful to host. Based on the data of phylogeny in trypanosome, the origin, phylogeny and evolution of trypanosome, coevolution between host and trypanosome parasite, and present existing problems were reviewed in this article.