Abstract: In the early stage of the construction of electricity spot markets, identifying the collusion bidding of generators is an important link to effectively prevent the actual occurrence of collusion behaviors of power producers. Based on the market sharing,the generators are classified into Cartel-type generators and competitive-type generators. For the Cartel-type generators, a method of collusion bidding based on ordered Logit model is proposed. Firstly, based on the game theory, the factors affecting the bidding of generators are analyzed, and the bidding regression equation of generators is constructed. Then, the Chow test is used to determine whether there is a difference in the degree of the influence of the bidding influence factors on the bidding behaviors of Cartel-type generators and competitive-type generators. If there is a difference, the ordered Logit model of Cartel-type generators is established, and the likelihood ratio test is used to determine whether there is a difference between the high-priced sequence and the low-price sequence of the Cartel-type generators, thereby demonstrating the possibility of collusion bidding of Cartel-type generators. Finally, the proposed method is applied to an electricity spot market in a region, and the case study results show that at a significance level of 5%, which means a possibility of collusion bidding of Cartel-type generators.