The movement of the sliding guide mechanism causes an offset and deflection of the lens due to the clearance fit between the sliding guide mechanism and drawtube. Based on the theory of flexible body kinematics, the motion simulation of the sliding guide mechanism at different motion postures, length-diameter ratios and arrangement positions of the guide pin and lens, was analyzed, which influenced the lens offset and deflection. The nested steering mechanism was simulated and analyzed to verify the feasibility and meet the practical requirements of the zoom optical system. Accordingly, the infrared continuous zoom lens sliding guide mechanism was designed and fabricated. Subsequently, the zoom process of the lens was imaged. It was demonstrated that this simulation analysis provides an effective method to enable the structural design and research of infrared zoom lens.