The utility model discloses a multi-use spray gun of the steam car-washing machine. The utility model is used to wash all kinds of locomotives and overcome the inconvenient operation deficiency of the spray gun for the present steam car-washing machine. A steam passage and a cleaning liquid passage are provided in the gun body. A bottle of the cleaning liquid is provided on the gun body. One end of the steam passage is provided with a steam exit. The steam exit is arranged at the gun mouth. The other end of the steam passage is provided with a steam inlet. The steam switch which controls the opening and closing of the steam passage is arranged in the steam passage. A trigger which controls the on and off of the steam switch is arranged on the gun body. One end of the cleaning liquid passage is provided with a cleaning liquid exit. The cleaning liquid exit is arranged at the gun mouth. The other end of the cleaning liquid passage is connected with the bottom of the cleaning liquid bottle. A micropump is arranged near the bottom of the cleaning liquid bottle. The gun body is provided with a jiggle switch which is used to control the on and off of the micropump power. The utility model provides the operative convenience for car washing.