The Mesozoic Jurassic reservoir of Xishanyao formation in the Niujuanhu area of Santanghu basin has typical abnormal low pressure reservoir characteristics, reservoir reaches a maximum depth during late of Late Cretaceous, at this point the lower Lucaogou source rocks evolution reached the maximum extent, with the oil and gas continued to fill the reservoir, when the formation pressure reaches the maximum, up 30.33~50.74MPa.