Abstract: Larger storage spaces can be formed within and nearby major faulted zones. The problem is if and in what degree they are sealing. In this paper,the pool forming probability of major faulted zones was discussed,and three signs used to discern a fault is sealing or not were suggested,that is,a)high abnormal formation pressure,b) water types and mineralization degree representing sealing environments and c) longitudinal multiple pay beds,pressure systems and water types. The three signs for discernment are fit for not only carbonate rock regions such as the Permian of South Sichuan area but also other clastic rock sedimentary regions. Except for the Tongtian Fault and denuded regions of gypsum salt layers in South Sichuan area,many major faults buried underground have good sealing performance and are favorable for the migration,accumulation and preservation of oil and gas.