Fluid potential is the key factor of distribution of hydrocarbon. The development of pressure in Upper Palaeizoic group in Yulin region was simulated by basin modeling technique. There are two recurrent processes of pressure development in Shanxi formation. The first occurred from middle Permian to early Jurassic, and the other took place from middle Jurassic to later Cretaceous. In later Triassic and early Cretaceous, there were two peaks of overpressure. The maximum value of overpressure surpassed 10 MPa. It took the same time as that of the hydrocarbon generation and the second peak of overpressure. From Paleogene to nowadays, gas diffusion decreased the coefficient of pressure from 1.4 to 0.8. Nowadays, the gas pool is located in the region of lower fluid potential in the period of hydrocarbon generation. It is suggested that paleo-fluid-potential controlled the distribution of hydrocarbon migration and accumulation in Yulin region.