The utility model discloses an 800hp mud pump unit adaptive to a -45 DEG C low-temperature environment. A diesel engine and a hydraulic transmission device are connected with an angle transmission case through a coupling; power of the angle transmission case is input through a flange; the power is transmitted to an output shaft through a spiral bevel gear; two ends of the output shaft are both provided with pulleys connected with a mud pump through joined narrow V-belts. The bottom of each of the diesel engine, the hydraulic transmission device, the angle transmission case, an oil sump of the mud pump and a spray pump water tank is provided with an explosion-proof electric heater and a temperature controlled switch correspondingly. The angle transmission case is further provided with an air-cooling oil cooler. A stain collecting plate is disposed on the top of a skid base; the section of the stain collecting plate is V shaped; an insulation layer is arranged on the inner side of the skid base; a heating vapor coil is arranged on the stain collecting plate; a skid base holder is arranged at the bottom of the skid base. The 800hp mud pump unit allows overall transportation, quick conveying, is convenient to convey, convenient to maintain and high in environmental adaptability, is suitable for use in the -45 DEG C low-temperature environment and has promising market prospect of popularization and application.