Abstract: Human African trypanosomiasis is caused by the infection of Trypanosoma brucei gambiense or T.b. rhodesiense， while another morphologically identical subspecies， T.b.brucei， and other closely related species， T.equiperdum and T.evansi， are considered not infectious to human. This is highly related to the trypanosome lytic factor （TLF） found in normal human serum （NHS） and the serum resistance-associated （SRA） protein of trypanosomes infectious to human. We reviewed the research progress in TLF and its role in trypanosome lysis as well as the mechanism of SRA against the TLF.

Key words: Trypanozoon, Trypanosome lytic factor （TLF）, Serum resistance-associated protein