Science of Security 2022 - At present, production and daily life increasingly rely on the Internet of Things, and the network security problem of the Internet of Things is becoming increasingly prominent. Therefore, it is extremely important to ensure the network security of the Internet of Things through various technical means. The security of IoT terminal access behavior is an important part of IoT network security, so it is an important research object in the field of network security. In order to increase the security of IoT terminal access, a security evaluation model based on zero trust is proposed. After the simulation performance test of the model, it is found that the model shows excellent detection ability of malicious access behavior and system stability in different network environments. Under the premise that some network nodes are infected, the model proposed in the study still shows a significantly higher ratio of trusted nodes than other algorithms, The research results show that the model can improve the security level of the Internet of Things network to a certain extent.