The invention particularly relates to an isolater belt pulley capable of reducing resonance frequency through axial mixing adjustment, and belongs to the technical field of automobile accessories. Thebelt pulley comprises a belt installation part and a core shaft, the belt installation part is movably installed on the core shaft in a circumferential direction, the belt pulley further comprises anaxial limiting part, the axial limiting part is arranged so as to enable the belt installation part to move in the axial direction relative to the core shaft when the belt pulley rotates in the circumferential direction. According to the belt pulley, one-way transmission capability is provided, the outer ring of the belt pulley changes along with the fluctuation of the tension of a belt, the tension of the fluctuation is absorbed in an axial adjustment mode, the resonance frequency is reduced to be less than a normal working range or below, so that the service life of a generator system and the service life of the belt are prolonged, and the oil consumption of an engine is reduced.