Abstract: In order to reduce the optical axis drift of the mechanical compensating continuous zoom thermal imager during zooming, on the basis of the researches on the structure and principle of the continuous zoom infrared thermal imager, we optimized the initial system parameters to ensure the smoothness of the compensation group moving curve, and designed the cam curves of the zoom group and compensation group to be non-linear, which could ensure the uniformity of the focal length and reduce the optical axis drift caused by the rotation of the cam. For systematic errors, we fitted the axis drift curve by using trigonometric functions and polynomials, and took advantage of dynamic software compensation techniques to compensate the optical axis drift. The results show that the optical axis drift can be controlled within about a charged couple device (CCD) pixel size in this method. This way has strong robustness ,which can provide a certain reference value for similar zoom lens design.