Q-switched Nd:yag laser applies the explosion effect of laser, which can permeate the cuticle efficiently to the pigment mass in the derma. The laser pulses in nanosecond range with very high energy. When the laser is absorbed by according pigment, the pigment mass expands quickly and breaks into particles which are eliminated through phagocytes. Whereby the shattered pigment is absorbed by the body and excreted out. Gradually the pigment becomes lighter and lighter till disappearing.