Abstract: The main forming forming mechanism of the abnormal fluid pressure in Wuyang depression are studied through analyzing the distribution characteristics and combining with the specific stratigraphic structure of interbedded saltand mudstone and the specific characteristics of salt rock barrier layer in the depression. Genesis of the shallow abnormal pressure system is unequilibrated compaction resultcd from rapid subsidence and compressive stress incrcasement resulted flom structural compression, genesisof the medium abnormal pressure system is compressivestress increasement in uncompacted mudstone due to that salt rock barrier kept fluids in mudstone from discharging during subsidence; genesis of the deep abnormal pressure system is the result of rapid subsidence of the depression,pressure increasement due to groundwater heating-up and organic materials changing into hydrocarbon.