Since the knowledge resource becomes an important part of enterprise resources, the knowledge management risks could significantly affect the enterprise operation efficiency. Controlling knowledge management risks is one of the enterprise management tasks; the managers and researchers focus on how to effectively evaluate the risks. This paper aims to solve this problem and puts forward an evaluation model of the uncertain risks of knowledge management. Based on set pair theory, a model is established to identify the knowledge management risk. Through the concept of connection number, knowledge management risk is divided into five levels. Meanwhile, the development trend of knowledge management risk is classified into same tendency, equal tendency, and contrary tendency by the concept of set pair theory. The application of this model is empirically verified with Chinese enterprises. Through both static and dynamic evaluations of the knowledge management risk, this paper can effectively analyze risk development trend and provide decision support for the enterprise manager about the uncertain risks of knowledge management.