On the basis of continuous medium theory, computer simulation analysis of metal-powder injection molding was carried out with the help of FLOTRAN hydro-analysis module of ANSYS software. The effects of the gates with different dimension and location were testified. The impact of gate system on the filling process is discussed. The dynamic display of the flow leading edge in the cavity, and temperature field of the melt were researched. A result was obtained that we can modify the design of runner system if we make a full use of existing equipment resource.