Tengbo base groove has a unigue pre-loaded and anti-release structure, so that the plug-in unit is locked in the groove, not blown out. By eliminating internal and external roling and plate locking, not only the processing is reduced, but also the damage of coating is avoided, as a result the valve seat is stable in performance and beautiful in appearance. The spring ofthe seat is mounted at the tee head of the base, which can effectively avoid the dirt in the medium to impact on the spring. The effective thrust at the back can be controlled to be less, the valve can be opened and closed easier under total pressure difference.