A horizontal machining center of constant pressure workbench structure was introduced.Horizontal machining center is a high degree of automation in machine tools, and one of the integrated processes of machine tool. Application of traditional fixture to a certain extent, restricted the full realization of the superiority of the horizontal machining center, using the workbench oil technology, to provide power for the fixture, and to ensure the completion of the fixture operation, the using scope of horizontal machining center and the degree of automation were increased. This type of fixture in practice proves the technology be more reliable in application，simple and reasonable in design and very practical.