Based on the analysis of the structure and the working principle of the threaded cartridge valve, a theoretical calculation model for the clearance variation between the sleeve and the spool under the effect of tightening torque and thermal stress was built. The clearance changing rules were analyzed by theoretical calculation, and the calculation model was validated combining with the finite element analysis results. The calculation model can be used to analyze the performance of the threaded cartridge valve under heat stress, and it has a certain guiding significance for designing and using of threaded cartridge valve.