The method of regulating the concentration of diphenol propane solution in two-step crystallizing purification process includes dissolving the phenol-diphenol propane adduct in phenol into solution, setting solution circulating pipeline, measuring the crystallizing temperature of the solution in the circulating pipeline to obtain the solution concentration, and regulating the concentration and measuring the crystallizing temperature repeatedly until reach the solution concentration for the second crystallization. One corresponding apparatus is also disclosed, which includes a dissolving kettle, a pump, a second crystallizing kettle, a pipeline with branch pipe between the pump and the second crystallizing kettle, a crystallizing temperature measuring control valve, etc. Owing to the excellent corresponding relationship between the material concentration and the crystallizing temperature, the method has high measurement precision and fast measurement speed.