In view of the importance of proper gate location and size in mould design process, with the basic analog theory for simulating the filling process of plastic melts in the cavity of injection moulds, injection moulding CAE technology was proposed for the optimum design of gate location and size. Based on Moldflow software, the analysis process of the best gate location and size was stated. The gate location and size and injection moulding technical parameters were optimized in this paper by example. The optimal rectangular gate dimension was 5mm×2.5mm, filling state was fine, filling time was reduced from 0.72s to 0.69s. It was resulted in products of high previewed quality, reduced the cost of production and enhanced the competitive power of mould enterprises.