On questions of long mould design cycle about reciprocating skeleton oil seal,started with the mould design by studying the reciprocating skeleton oil seal,the determination method to the key mould parting line was researched.The deformation law about residual glue tank and ejector and relative wall thickness and other key parts were analyzed,and the mathematical model was established.The top-down modeling method was used to establish the overall assembly and parts model.According to the mold design rule,the key features of each part of the mold cavity and its parting line were extracted from the geometric features of the oil seal 3D model,and the characteristics of the inner parts of the template parts were formed.By using these features to remove the internal characteristics of the various parts of the assembly structure,the mold cavity structure characteristics were got,and the mold design was completed.The design method can realize the automatic deformation of the skeleton oil seal mould with the size of the oil seal,which greatly improves the design efficiency.