The invention relates to a method for removing a high-pressure heater based on a waterside bypass to participate in primary frequency modulation of a unit. According to the method, an economical operating mode of full opening of a high-pressure control valve is kept, the high-pressure heater is rapidly removed by the aid of the waterside bypass of the high-pressure heater when grid frequency is reduced to a set threshold value, so that stored energy of steam extraction of the high-pressure heater is released, a function of rapid loading through primary frequency modulation is realized. Compared with the prior art, the method can realize economical operation and meet the requirement for the primary frequency modulation, has great significance for a large number of throttling steam distribution units, and can further promote energy conservation and emission reduction of a thermal power generating unit.