The invention discloses an adjustable input power type arc heating plasma spraying gun. The adjustable input power type arc heating plasma spraying gun comprises a positive pole, an inner insulating sleeve, a negative pole, a driving screw, an end cover and an outer insulating sleeve. According to the adjustable input power type arc heating plasma spraying gun, the space between the positive pole and the negative pole is adjusted to adjust the input power of the spraying gun, and therefore the input power of the arc heating plasma spraying gun can be adjusted in structure; in addition, a negative- and positive-pole water cooling integrated loop is adopted to avoid the difficulty at dismounting, mounting and leakage detection due to complex water cooling systems; in addition, the positive pole water cooling surface is the same as the telescoping expanding surface of a positive-pole nozzle, so that the water cooling contact area is increased; the water cooling system of the arc heating plasma spraying gun is simplified to the maximum, and therefore, the cooling efficiency is increased.