A paper change control system of a paper stacking board of an automatic printing machine comprises a laser, wherein an emission optical path of the laser is provided with a collimating lens, light emitted from the collimating lens is irradiated to the board surface of the paper stacking board, the angle formed between the light and the board surface is 45 degrees, produced reflected light enters an imaging lens and is received by a linear array CCD arranged behind the imaging lens, an output signal of the linear array CCD is connected into a processor, the processor outputs two paths of controls signals which are connected with a paper change mechanism and a paper stacking board motor respectively, and the processor outputs a drive signal to the laser at the same time. By the paper change control system, displacement of the paper stacking board can be accurately detected out, then corresponding automatic adjustment is carried out, and manual operation is not required.