With the analysis of the gastesting data, the Upper Paleozoic reservoir temperature in Yanchang area has been calculated. Based on thermal evolution indicators and palaeogeothermal recovery, it is indicated that the Upper Paleozoic source rocks have reached the maturity stage and the overmaturity stage. The paleogeothermal gradient in different period is discussed. The erosion thickness of the formation in this region was recovered. The thermal evolution history of Upper Paleozoic in Yanchang exploratory area has been reproduced. The main sedimentation period is Late Triassic(226～208Ma). The Upper Paleozoic source rocks reached the maturity stage in Early Jurassic and reached the high maturity stage in Late Jurassic. The main gas generation period of the Upper Paleozoic in Yanchang area is from Late Jurassic to Early Cretaceous.