The invention discloses a high-precision simulation inter-cooling constant temperature apparatus for an automobile engine testing stand. The high-precision simulation inter-cooling constant temperature apparatus for an automobile engine testing stand includes a water/air heat exchanger which is communicated with the outlet and the air inlet of a supercharger of an engine and forms an air circulation channel, wherein the medium water outlet of the water/air heat exchanger is communicated to the medium water inlet of the water/air heat exchanger through a liquid storage tank, a tee ratio adjusting valve, a circulating water pump and a flow control valve successively; the medium water outlet of the water/air heat exchanger is also communicated to the other inlet of the tee ratio adjusting valve through the water/air heat exchanger through a pipeline; the heat exchange medium inlet of the water/air heat exchanger is communicated with a cooling water pressure water inlet, and a heat exchange medium outlet is communicated with a cooling water outlet; and an electric heater is arranged on the liquid storage tank. The high-precision simulation inter-cooling constant temperature apparatus for an automobile engine testing stand has the advantages of being small in the temperature fluctuation, being relatively higher in the heating speed, integrally improving accuracy and repeatability ofthe test, and saving energy consumption during the testing process.