There are serious cyber security threats in wind farm SCADA systems drinking a large number of embedded terminals with scarce computing resources, so a lightweight key management scheme needs to be designed. Security threats to wind farm SCADA system keys and types of system communication are analyzed. Lightweight key management schemes based on CL-PKC and CRT are proposed. In this scheme, we have completed the generation and distribution of device public and private keys and unicast session keys by CL-PKC, and the generation and distribution of group session keys by CRT, and give the process of key update and key destruction. The verification results show that the key management scheme secures the keys and is resistant to forgery, replay, interruption and tampering attacks. In addition, the solution has good forward security and backward security.