The invention discloses a pressure casting process of a motor rotor. The pressure casting process of the motor rotor comprises the following steps of mold confirmation; equipment confirmation; oil pump starting; confirmation of equipment parameters; confirmation of tools; opening of a release agent pipeline valve; cleaning up of aluminum skimmings on a pressure injection plunger; cleaning up of aluminum skimmings on a mold cavity and a parting surface; mold assembly; pressure injection; workpiece taking; cooling; and mold releasing.