The hydraulic spool valves are usually equipped with viscous heating effect in the entire operating process, which has significant impact on controllability of spool valve. In order to present the thermal fault of spool valve, the integrated thermal model for spool valve with fit clearance was established, numerical investigation for thermal characteristics of spool valve had been carried out by settling integrate thermal model with help of Conjugate Heat Transfer Module and Particle Trajectory Module in COMSOL code in this thesis. The result indicated that, the high temperature mainly appeared at the zone with larger velocity gradient and the surface of spool groove impacted by the high velocity flow. The non-uniform radial thermal deformation occurs on matching edges of spool valve caused by temperature gradient. The solid particles gather densely in pressure groove more easily after deformation. By these token, the radial thermal deformations of matching edges provide positive effect on the contaminant lock. These verdicts provide the engineers with a visualization comprehension for the phenomenon of spool thermal clamping.