The processes developed for molding plastics and the different processing properties of the plastic lead to different loads, which must be taken into consideration not only in the design but also in the selection of material required for molds. Steel has the ideal qualifications, because its properties can be modified by alloying elements, special production processes, and heat treatment ,and it can be adjusted to various requirements. We will choose the proper steel material according to mould design and tooling process to satisfy demands.