Abstract: This paper introduce the design and process of injection mold base on the example of Plastic mold design of clothes racks and it’s typical mold components process by NC. At first, under the pieces of plastic materials and process characteristics with software pro / e for model analysis, then choose injection molding machine and to determine the number of cavity, then determine forming programs : overall structural design, type design, gating system design, ejection mechanism design, design of the cooling system .Finally checking processing parameters of the injection molding machine, including the injection volume, clamping force, injection pressure, thickness and injection mold machine closure height.Next using the right software MasterCAM molding parts NC to determine tool paths and processing methods, Simulation of their processing 。