The digital simulation of the slide valve was carried on using the solver of ADINA. The hydraulic clamping of spool valve was researched with digital simulation method. The relationship between the gap characteristics of spool valve and lock force was researched and how the rectangular equalizing tank to reduces lock force. The lock force pushes the spool move to sleeve, which may lead to spool be clamped. Compared with the offset, the influence of cone angle to lock force is greater. The lock force is reduced effectively after the rectangular equalizing pressure tanks are opened. The optimal location and reasonable structure size of equalizing pressure tanks are gotten by studying how the location and structure size of equalizing pressure tanks reduce the lock force.