Abstract: In this work, we designed a large and hot runner injection mold of car rear door according to its structural characteristics and technical requirements. A reasonable gating system was determined on the basis of the mold flow analysis. The shrinkage problem was well solved by controlling the diameter of hot nozzle gate. The drawing and casting problem of hot nozzle and the gate residue were solved through separating the cooling channels around the hot nozzle. The results indicated that the molding cycle was controlled within 60 s, and the efficiency was improved by about 8 %, confirming that the mold structure was reasonable and advanced.