Slider is one of the most important parts in High-Speed Horizontal Machining NC center, it plays a great role in the performance of static and dynamic. In order to assure the working accuracy and dynamic characters, slider must be analyzed to verify the reasonable of original design. According to the structure of slider and based on the theoretical and finite element simulation analysis method, a more reasonable boundary condition is carried out. To be noted that in this paper a method using the conception of combination is introduced. On the other hand the counterforce can be more accurate than before and it makes the following analysis easier.