The oil sealing belt of the rectangle oil pocket makes full impact on the dynamic and static characteristic of the closed-type liquid hydrostatic slide. Regarding the closed-type liquid hydrostatic slide adjusted by the speed control valve, the mathematical expression on the dynamic and static performance of the slide and the oil sealing belt of the rectangle oil pocket is derived, and the change of the dynamic and static performance of the slide in case of changing in width of the oil sealing belt is presented. The results showed that on the premise of not being crushed, the narrower the oil sealing belt, the better dynamic and static performance of the slide. The best changing scope of the oil sealing belt is presented in this paper. The proposed research analyzesd quantitatively the influence on the oil sealing belt of the dynamic and static performance of the slide, and provides a basis for the designing reasonably the oil pocket in the practical engineering.