Computer aided design (CAD) is used in the design of complete sets of electrical field which is divided into mechanical CAD and professional electrical CAD (ECAD) phase. At present, most commercial ECAD software is products based on the mechanical CAD software secondary development. On the one hand, keeping mechanical CAD design function, in order to realize the mechanical design requirements; On the other hand, to realize the electrical professional design features through the secondary development. This paper tries to analysis of complete sets of electrical system design process, adopts the object-oriented technology to build a independent of the underlying general CAD platform, with different general CAD platform integration, on the basis of the open electrical symbol library that can expand complete sets of electrical auxiliary design framework, implements under the framework system of electrical secondary principle design related function, and verifies the feasibility of the framework.