Abstract. Model security for collaborative product development in a networked environment (or called networked manufacturing, grid manufacturing, and cloud manufacturing) is an important and also challenging research issue. An encryption based partial sharing approach for CAD models has been developed and presented in this paper. First, a random invertible decimal matrix to support the encryption approach is proposed, with which parts of a CAD model can be selected flexibly by the model owner for encrypting by different keys; Second, in order to guarantee the security, a dual-key mode and a key based authorization mechanism are proposed. Based on the model, different levels of security are achieved based on different key spaces, and the key based authorization mechanism is used for the model owner to control the partial access of the CAD model flexibly.