The injection products should not be too thick and when necessary the stiffening rib can be added to reduce wall thickness; the wall thickness must be kept as uniform as possible and the shape and structure should be simple and symmetric; the parts with insufficient shrinkage compensation can be approached from structure of products, whereby the section of runner can be enlarged by adding stiffening rib to make it easier for shrinkage compensation; on important surface of products, structural intersection should be reduced as much as possible so that hot spot thereon can be reduced accordingly; at positions such as hot spot where depression may occur, thickness of cavity section can be properly increased through reverse compensation to counteract the shrinkage depression value; decorative patterns can also be designed at positions with shrink mark to cover up the visual defect caused by surface depression.