The invention discloses a method and process for stabilizing online acid sediment of soybean protein. According to the method, a hydrochloric acid constant-pressure buffer tank is arranged among the output end of a cam type rotor pump, the output end of a hydrochloric acid metering pump and the input end of a static mixer, and opening of the hydrochloric acid metering pump is controlled by a pressure remote controller, so that hydrochloric acid in the buffer tank is kept at constant pressure; a flow switch and a micro-flowmeter are arranged at the outlet end of the hydrochloric acid constant-pressure buffer tank; and an SK-type structure is adopted inside the static mixer. The method is simple in method and convenient to operate, and has the characteristics of eliminating the pulse phenomenon of the hydrochloric acid metering pump generated in the delivering process and the phenomenon that materials are not uniformly deposited or mixed due to the structure defect of the static mixer.