The invention relates to a casting part grinding device capable of lowering the temperature. The device comprises a grinding box body and a support frame, and the grinding box body is arranged at the upper end of the support frame; a heating device and a grinding roller set are arranged in the grinding box body, and the heating device is located in front of the grinding roller set; a material inlet and a material outlet are formed in two side walls of the grinding box body respectively; a first conveying belt and a second conveying belt are arranged at the two sides of the grinding box body respectively, the end, close to the grinding box body, of the first conveying belt passes through the material inlet, extends into the grinding box body and gets close to the heating device, the end, close to the grinding box body, of the second conveying belt passes through the material outlet, extends into the grinding box body and gets close to the grinding roller set, and the horizontal position of the second conveying belt is lower than that of the first conveying belt; a water spray device is arranged over the position, corresponding to the second conveying belt, of the inner side of the grinding box body, and a waste water collector is arranged under the position, corresponding to the second conveying belt, of the inner side of the grinding box body. By means of the device, a casting part can be heated and ground automatically, the grinding efficiency is high, the temperature can be lowered, dust can be removed, and the service life is long.