The invention provides a simulation method and a simulation device of influence on automobile water pump pressure pulsation by a blade tip clearance, wherein the simulation method comprises the following steps of model establishment, grid division and monitoring point arrangement. A fluid domain of an automobile water pump comprises a pump cavity, the blade tip clearance, an impeller, a spiral case and a water outlet pipe; grid division is performed on the automobile water pump by adopting a hybrid tetrahedron-hexahedron non-structural network; multiple monitoring points are arranged on a pressure surface and a suction surface of a blade respectively; and multiple monitoring points are circumferentially arranged on the spiral case. The simulation method and the simulation device provided by the invention can more accurately find a main frequency of the influence on automobile water pump pressure pulsation, are convenient to find a relationship between the blade tip clearance and the pressure pulsation on the blade and the spiral case and can simulate a relationship between the thickness of the blade tip clearance and the respective pressures on the blade tip clearance, the spiral case and the blade tip clearance, a relationship between the thickness of the blade tip clearance and the flow rate in the spiral case, a relationship between the thickness of the blade tip clearance and the vortex strength in an impeller flow passage, a relationship between the thickness of the blade tip clearance and the vortex strength at the outlet of the spiral case and the like.