In order to further deepen the study of oil and gas accumulation and to point out the direction for exploration of the limestone reservoir in the 4th member of the Shahejie Formation of the northern step-fault zone of Shaojia area，the transport system and the model for oil and gas accumulation were studied deeply based on the analysis of petroleum geological characteristics and according to the theory of petroleum geology and differential hydrocarbon accumulation theory. The results show that 4 kinds of transportation systems are found in the limestone reservoir in the 4th member of the Shahejie Formation of the northern step-fault zone of Shaojia area. The first one is the primary migration system where hydrocarbon source and reservoir rock connected laterally at the fault upthrown and downthrown. The second one is the vertical migration system where primary migration occurs in the overlying medium to high maturity source rocks. The third one is the vertical deep fracture migration system where secondary migration of hydrocarbons occurs. The fourth one is the lateral unconformity migration system for secondary migration of hydrocarbons. There are 3 kinds of oil and gas accumulation models under the influence of 4 kinds of oil and gas transportation system. In the first model，oil and gas migrate vertically and are accumulated in the structural trap. In the second one，oil and gas are accumulated in the lithological trap after migrating laterally for a short distance. The third one is the differential hydrocarbon accumulation model that hydrocarbons are trapped after migrating laterally for a long distance.