Abstract: An automatic light intensity compensating device of a surgical light includes a suspension or support system and one or multiple light heads carried on the suspension or support system. Each of the light head includes a housing, one or multiple grips mounted to the housing for hand holding and moving the light head to a desired position, one or multiple light sources mounted in the housing for illumination, a focus adjustment mechanism for adjusting the focal length of illumination, a focusing detection mechanism for detecting a position of the focus adjustment mechanism within a variation range, and an automatic illuminance compensation device, which automatically increases or decreases luminance of the light source according to the position of the focus adjustment mechanism.