The utility model relates to an air winch for petroleum drilling. The air winch comprises an air motor, a speed reduction device and a rope reeling roller, and air inlet of the air motor is connected with an air source pipeline through an air inlet pipe and an air inlet ball valve, an air exhaust port of the air motor is communicated with the atmosphere through an air exhaust pipe and a muffler, the speed reduction device is provided with a manual brake which brakes an output shaft of the speed reduction device, the air motor, the speed reduction device and the rope reeling roller are of a split structure, the air motor and the speed reduction device are respectively supported on a motor machine frame, the two ends of a spindle of the rope reeling roller are supported on a roller supported respectively through bearing seats, the motor machine frame and the roller support are respectively supported on a common base, an output shaft of the air motor is fixedly connected with an input shaft of the speed reduction device, the output shaft of the speed reduction device is connected with one end of a roller spindle of the rope reeling roller, and the other end of the roller spindle is provided with an air brake. The air winch is convenient to maintain, the rope reeling roller can independently brake, so that heavy objects are prevented from falling during malfunctions.