A method for automatic exposure compensation is disclosed. A shutter is activated and the environmental brightness is detected using a sensor. An exposure value is calculated according to the detection result to obtain a default exposure time. It is determined whether the exposure value is equal to a normal value. If not, a compensation value is calculated based on a shutter-closing curve and a compensation operation is thus executed. Thus, an exposure signal is generated by advancing a first predefined time or postponing a second predefined time, enabling the amount of exposure time to be equal to the addition or subtraction of the default exposure time and the first predefined time.