Abstract: With the rapid development of the power Internet of things, it is difficult to carry out effective risk assessment due to a large number of network security risks. In view of this situation, this paper proposes a security risk assessment method based on factor correlation. Firstly, this method extracts the security risk elements of the power Internet of things, and puts forward five key security elements. Secondly, the process design is combined with the thought of DEMATEL-ANP, and expert decision is integrated to quantify the impact relationship and intensity between security objectives and measures. Finally, based on the process, several security schemes of a system are analyzed with examples, and the value at risk is obtained and its application is verified, which proves that the method can solve the problem of correlation of risk factors and risk quantification.