Few researches of paleogeothermal gradients in the northeastern area of Sichuan Basin has been reported. The paleogeothermal gradients during the key period of hydrocarbon maturation were investigated by EasyRo modeling in the light of the available measured reflectance data of well samples from Puguang Gas Field in this area. The result shows that among four modeled REasy values, the one that modeled with 3.0℃/100m of paleogeothermal gradient during the Triassic-Early Cretaceous period may match well with its measured Ro and Rb values. Therefore, a simplified model of paleogeothermal gradient, i. e. 3.0℃/100m (＞96Ma)-2.8℃/100m (65Ma)-2.2℃/100 m (0Ma), was suggested for the northeastern part of Sichuan Basin. It was believed that this model can give a good explanation for the geochemical characteristics of natural gas in this area.