Using freeze-dried pitaya peel and pulp samples as raw materials, response surface methodology was used to optimize the cellulase-ultrasonic extraction process of pigment from pitaya peel and pulp. The optimal extraction process of pigment from pitaya pericarp was as followed: extraction time 24 min, extraction temperature 39 ℃, ultrasonic power 325 W, ethanol concentration 23%, the yield was (81.661 3±0.762 0) mg/100 g; The optimum extraction conditions of pigment from pitaya pulp were as follows: extraction time 34 min, extraction temperature 41 ℃, ultrasonic power 315 W, ethanol concentration 23%, and the yield was (278.660 4±1.084 2) mg/100 g.