A locking mechanism for a nozzle in an inflatable object includes a membrane member having a ledge extending outward for securely engaging with the inflatable object, a nozzle seat having a flange to firmly engage with the ledge, a positioning element having two arms, a cap having a lifting mechanism to elevate location of the positioning element, a descending mechanism to descend the location of the positioning element and a sealing part integrally formed and a sealing part integrally extending from the flange and a core having a directing rod securely connected to the positioning element so as to move with the positioning element accordingly and a sealing flange formed with the directing rod such that movement of the core together with the positioning element allows the sealing flange to selectively and sealingly engage with the sealing part of the nozzle seat to block airflow.