The ball of trunnion mounted ball valve is fixed, supported by a fixed trunnion and sliding bearing.When closed, the ball will not move by the action of the medium, the structure ensures the ball maintain on the exact central position even under high pressure, which can improve the operation performance; the seat is spring loaded, the spring push the seat to the ball to guarantee a good bi-direction sealing; with drain valve, the body cavity release the medium out; shaft is anti-blow out to avoid leakage; bearing of low friction coefficient minimum the torque value for an easy open and close; stem in touch with body avoiding large amount of static generate.