The invention provides a comprehensive evaluation method and system for primary frequency modulation performance of a unit based on a comprehensive weighting method, and the method comprises the following steps: building a unit primary frequency modulation evaluation index system, and obtaining an initial evaluation index according to the unit primary frequency modulation evaluation index system;performing normalization processing on the initial evaluation index to obtain a final evaluation index; calculating the final evaluation index by adopting a subjective decision-making method to obtainsubjective weight and objective weight of the index; And calculating the comprehensive weight of the subjective weight and the objective weight of the index by using a least square method, and obtaining a comprehensive evaluation result of the unit according to the comprehensive weight. According to the method, a complete index structure is established, the comprehensive evaluation of the primaryfrequency modulation of the unit is obtained by combining a subjective and objective weighting method, the result is more comprehensive, objective and reasonable, the scheduling management departmentcan comprehensively analyze the primary frequency modulation performance of each unit in a power grid, a database can be conveniently established to manage and examine the units, and the supervisionand evaluation quality can be improved.