Abundant CO2 andN2 gas reservoirs and otherN2-bearing gas reservoirs are discovered in the Neogene and Quarternary shallow beds of Central Mud diapir Zone in Yinggehai Basin, South China Sea during recent 20 years´oil and gas exploration. According to geological and geochemical characteristics of N2, the N2 gas in this area can be divided into three types in genesis, i.e. the atmosphere genesis, the crust organic genesis and the crust-derived organic-inorganic-mixed genesis. Combined with results from the nitrogen-producing experiments under T-and P-controlled thermal simulation and the characteristics of partial enrichment in plane and layering and zoning enrichment in vertical, it is determined the N2 gas is tracked to the mixture of the N2 that mainly yielded from Pliocene and Miocene marine gas source mudstone during different stages of maturation with the N2 that formed from physical and chemical actions and rock degassing.