Aimed at the middle and high pressure system, because spool valve body and valve cover with smaller matching gap, and got stuck during application, the three-dimensional (3-D) Computational fluid dynamics (CFD) models and steady-state FEA thermal models were established separately. By using Thermal solid-fluid coupling methods, the phenomenon of viscous heating effect caused the fluid temperature increasing and the spool deformation were analyzed, and the temperature and distortion of the spool valve in the different opening and different spool materials were obtained. The results provide reference for calculation and design of the hydraulic spool valve.