Based on a visible and infrared dual band co channel imaging optical system,a dual band zoom compensation method is studied. According to the zoom and the mechanical passive compensation theory,the difference of visible and IR dual band zoom ratio is compensated. Combined with multiple configurations in ZEMAX,the multiple feature points are obtained by adjusting and optimization,and the change curve of focal length with the shift change of zoom group is calculated. The results show that the difference of dual band zoom ratio is small in this system,and it can achieve visible and infrared dual band zoom at the same time.