Abstract: In this paper,polyacrylamide gel electrophoresis was used for analyzing and determing peroxidases in leaf blades of Ulmus pumila,Ulmus pumilavar,Ulmus laevis and Ulmus densa,and getting peroxidase bands of four elms. Then, the sequence analysis method was used to identificate the differences of four kinds of elms. At the same time,comparison was made among the shape characteristics of four kinds of elms,and their discrimination and classification work was also done.