Abstract: In this paper the research results of the top gap slit now at reversed tainter valve on lock with high lift are presented, which include: the study of the slit now in 1: 1 slice model and its theorem, alternative tests in depression model on different air - entrainment position of the culvert near the valve, the researches about means of top seal aeration and its application on two locks. Prototype observation indicates that the top seal natural aeration can eliminate or greatly reduce the top gap cavitation and significantly improve the operation conditions of lock.