Aiming at the requirement for mechanical limiting position of remote depth setting unit of a torpedo , this paper analyzes the structure and working principle of the mechanical position limiter of transmission gear in the remote depth setting unit.This structure is designed to use worm gear transmission mode. Based on kinematic analysis and mathematically modelling , the movement attitude and tracks of the diagnostic parts are described quantificationally , and the important parameters which affect the limiting position of the diagnostic pa时s are analyzed. The result shows that this structure can meet the requirement for the mechanical limiting position of torpedo setting depth calibration. The research can provide a reference for design and application of similar structures.