A kind of pressure control mechanism of suction unit,Comprising an ontology and a piston body,The ontology has an accommodating space,The accommodating space system is connected to two casings,And there is an opening,The piston system axially slides the what accommodating space and two casings is made to be conducted with the accommodating space or mutually close,It is wherein to be provided with a flexible stopping leak part between the piston body and the opening,One of flexibility stopping leak part system protrusion setting what piston body radial surface,The flexibility stopping leak part has an outer convex binding face,The outer convex binding face system will not be deformed when radially an inner wall of the fitting what ontology what accommodating space and what piston body axially slide,To maintain good air-tightness,Carry out pumping operation can glibly.一種抽吸裝置之壓力控制機構，包含一本體及一活塞體，該本體具有一容置空間，該容置空間係連通二個套管，且具有一開口，該活塞體係軸向滑移於該容置空間而使該二個套管與該容置空間相導通或相封閉，其中該活塞體與該開口之間係設置有一撓性止洩件，該撓性止洩件係凸出設置於該活塞體之一徑向表面，該撓性止洩件具有一外凸弧形貼合面，該外凸弧形貼合面係徑向貼合於該本體於該容置空間的一內壁面而於活塞體軸向滑移時不會產生變形，以維持良好的氣密性，藉此使抽吸作業可流暢地進行。
