Aiming at the problem that the current market power evaluation of generators ignores the uncertainty and ambiguity of the index data, a comprehensive evaluation method of generators' market power based on the combined weighting and trapezoidal cloud model is proposed. Firstly, the method establishes the market power evaluation index system of power producers, and uses the combination weighting method to obtain the weights of each index. Then, the trapezoidal cloud model is utilized to calculate the membership degree of each index to each level, and the evaluation degree vector is obtained. Combining the combination weighting with the trapezoidal cloud model, the comprehensive evaluation of the power generation market power is realized according to the principle of maximum membership degree. The feasibility and accuracy of this method are verified by the case study.