The steady flow force characteristics of spool valve with flowin throttling have been studied through computational fluid dynamics （CFD） technique. The rule of fine gridgenerating and the method of calculating flow force through inlet and outlet velocity were given. The changing rule of steady flow force was calculated with methods of inlet throttling and outlet without throttling under different structural parameters of spool valve of annular area of the spool, annular length, and outlet length and angle in working condition, and their inherent mechanisms were analyzed. The study results show complexity in changing rule of steady flow force under this flow method, which can be used as a reference for spool valve design and analysis.