In order to study the influence of steel dissipators composed of flexural-and-shear yielding plates on the seismic performance of steel frame structures, a series of numerical models of two storey and one span steel frame structures which have diagonal braces were established by ABAQUS. The influence rules of different parameters on the seismic performance of the structure, such as the bearing capacity, energy dissipation capacity, the bearing capacity distribution and the energy consumption distribution between the brace and the braced frame structure, were explored. The result indicates that the steel frame structures mainly dissipated energy by the shear plate and then the bending plates yielding into the plastic stage; The hysteretic curve of the structures are in plump and the energy dissipation performance is excellent; In the early stage of loading, the horizontal bearing capacity and energy dissipation of the structure are mainly borne by the braces. In middle and late stage of loading, The flange connecting the beam with the gusset plate and the outer flange of the column foot appear stress concentration and enter into plasticity, the horizontal bearing capacity and energy dissipation of the energy dissipation brace gradually decrease, but still more than 50%. It is concluded that the plate yield energy dissipation brace can well share the bearing capacity and energy dissipation of the steel frame structure, which can be considered for practical engineering.