Abstract: Based on the characteristics of BMC materials, the principle of a warm runner injection process was discussed, and the main points of design for the BMC warm runner injection mold were analyzed. The manufacturability of the warm runner injection molding process was also studied in terms of two important injection-molding parameters: injection temperature and injection pressure. The results showed that the warm runner injection process could be applied in the injection molding process of plastic-packaged motor, in which the injection process without coagulation in casting system was realized and the deburring process was avoided for internal surface of the stator. This may brings considerably economic benefits.