Abstract: [OBJECTIVE] The study were progressed in order to pave the way for developing a specific-antigen-based assay and good quality vaccine for the E wenyoni control. [METHOD] The antigenic composition was identified tentatively with SDS-PAGE and western blotting after E.wenyoni was isolated from blood of cattle with E.wenyoni. [RESULTS] The result of SDS-PAGE showed that the molecular weights of E.wenyoni antigen covered 24kD~150kD. Nine domain proteins were clearly isolated, and their molecular weights were 141.34 kD, 107.27 kD, 86.03 kD, 68.05 kD, 56.21 kD, 44.30 kD, 32.99 kD, 28.89 kD, and 24.59kD, respectively. Three kinds of immunogenic protein were screened with western blotting, and their molecular weights were 147.31 kD, 49.03 kD and 35.72 kD, respectively. [CONCLUSION] E.wenyoni contains nine kinds of domain proteins and three kinds of immunogenic protein. They can be used for specific-antigens-based assay and protective antigens of good quality E wenyoni vaccine.