Abstract: SECS/GEM is a global communication protocol for semiconductor factories and semiconductor equipment. It is a manufacturing equipment protocol for data communication between equipment and host. Because SECS/GEM is designed to work in a closed network, SECS/GEM protocol does not provide any type of data security function. In view of this situation, a method of encrypting and digitally signing SECS/GEM data messages by using improved AES algorithm and ECC algorithm is proposed. The data part was encrypted by using AES algorithm, the AES key was encrypted by using ECC algorithm, and the data part was digitally signed. Experiments show that this method achieves the confidentiality and authenticity of data when receiving and sending messages.