In this paper, research was conducted on how the geometric errors of spool sleeve affected static pressure characteristics of a servo valve. A computer simulation model was established for a direct acting servo valve. The simulation time period of the one sinusoidal input was set as 500 seconds to avoid the dynamic hysteresis effect. A series of simulations took place to look for various values of clearance, overlap, and mismatch error. Pressure gain decreased as the clearance increased. It was also found that the overlap also affected the pressure gain and this was similar to the effect of clearance. Asymmetry of pressure plot got worse as the mismatch error increased. When more than one geometric errors appear simultaneously, the relevant effect of each geometric error was found to be superposed to each other. The simulation results showed that the geometric errors between the spool and sleeve is not related to the geometric errors.