The invention relates to a method for predicting heating peak modulation capacity of a heat supply unit. The method is characterized by comprising the steps of selecting at least one representative power plant, and performing data collection on heat supply design data, heat supply device conditions, industrial heat load and heating thermal load mediums, parameters and modes of the heat supply unit; through data analysis and theoretical calculation, determining design thermal load and the heat dissipation area of a radiator, considering impact analysis of temperature changes on building heat dissipating capacity and heating capacity, and predicting the heating period peak modulation load of the power plant. The method has the advantages of being scientific, rational and high in practicality. By utilizing the method, the maximum power generating and heat supply potential of the heat supply unit can be brought into full play, and the problem of difficulty in heating period power grid peak modulation is effectively relieved and solved.