To study the influence of human factors on power system reliability, this paper proposes a forced outage rate model based on Hidden Markov Model (HMM) which considers human factors and its human factor discriminant model. By analyzing the relationship between human factors and equipment repair, it divides the human factors scene into three types and optimizes the traditional equipment repair model. According to features of HMM model, the forced outage rate of HMM equipment is established. By using forward algorithm, it establishes human factors discriminant model. Practical examples validate the applicability of the forced outage rate model proposed in this paper and the correctness of human factors discriminant model. Human factors of the forced outage are distinguished, and targeted measures are taken to reduce equipment forced outage time and improve power system reliability. This work is supported by Special Science Foundation of Shaanxi Educational Committee (No. 16JK2174) and Science and Research Foundation of Xi'an Aeronautical University (No. 2017KY1222).