The invention discloses power stabilizing device and method for a laser device. The power stabilizing device comprises the laser device, a focusing lens, nonlinear crystal, a spectroscope, a landfill pond, a lambda/2 wave plate, a polarization beam splitter, a photoelectric detector and a controller, wherein an output light beam of the laser device is focused in the nonlinear crystal through the focusing lens; a small part of laser is converted into frequency-doubled light; a transmitted beam of the nonlinear crystal passes through the spectroscope; fundamental light is separated from the frequency-doubled light; the frequency-doubled light is introduced into the landfall pond; the fundamental light sequentially passes through the lambda/2 wave plate and the polarization beam splitter and is divided into two beams of light; transmitted light is output as main laser; reflected light enters the photoelectric detector; an output signal of the photoelectric detector enters a controller; and the controller generates a control signal to control the temperature of the nonlinear crystal, so as to stabilize the laser power. According to the power stabilizing method disclosed by the invention, the frequency-doubling conversion efficiency is changed by controlling the temperature of the nonlinear crystal; the frequency-doubling loss of the laser beams is changed; and fluctuation of the laser power is compensated, so as to reach the target of stabilizing the laser power.