Properly improve injection and dwell pressure as well as the injection rate to increase melt’s compression tightness; prolong time of injection and dwell (the freezing of gate should not occur too early) to realize sufficient shrinkage compensation;properly reduce melt temperature and properly raise mold temperature (whereas cooling should be reinforced at parts with thick walls) on the premises that the ejection quality and dimension precision of products after ejection are ensured; properly increase melt plastication quantity to ensure sufficient material supply and effective transmission of pressure; when depression occurs around the insert, the pre-warming temperature of insert should be increased to a certain degree. In addition, depression and shrinkage porosity which are unavoidable due to the structural property of products can be removed by adopting gas-assisted injection molding.