Abstract: The bidding behavior of power generation enterprises directly affects the clearing results of capacity markets, while the existence of oligopoly distorts the price signal of capacity markets and impacts the normal and healthy development of the market. Therefore, it is urgent to carry out in-depth research on the clearing results of capacity market under the influence of oligopoly power generation enterprises. This paper proposes a multi-leader Nash-Stackelberg game model to analyze the bidding behaviors of various power generation enterprises participating in the capacity market. As the leader of the game model, the power generation enterprise maximizes the net profit of its participation in the market through strategic quotation at the upper level of the model, while the capacity market clearing problem is the follower of the model. To solve the problem that the multi-leader game model is difficult to obtain the equilibrium solution directly, the shared-constraint method is used to extend the feasible domain of the proposed game model, and the KKT optimality condition is used to transform the game model into a generalized Nash equilibrium problem. In order to solve the global Nash equilibrium solution of the problem, the potential game model is reconstructed by constructing potential function. Finally, the actual data of a province in China are analyzed to verify the effectiveness of the proposed game model and solving algorithm. The results show that the decrease of the number of oligarchs or the increase of the share of the stock units of oligarchs will further aggravate the market monopoly phenomenon.