Quantitative study on oil generated overpressure is the key to calculating the dynamics of oil and gas reservoirs and determining the distribution of oil and gas. The existing calculation methods of oil generated overpressure are low in calculation accuracy and complex，which affect their rapid applications in exploration. In this study，according to the comprehensive analysis of hydrocarbon generation characteristics of type I organic matter，a new mathematical model of oil generated overpressure was established.The model was used to calculate the oil generated overpressure of Chang7 source rock in Xifeng Oilfield of Ordos Basin and analyze the influence of different parameters on the oil generated overpressure. The results show that the oil generated overpressure of Chang7 source rock in Xifeng Oilfield is 4.6-14.8 MPa，and the formation pressure is similar to the previous calculation results，which indicates that the model is highly reliable. The sensitivity analysis of rock parameters shows that the rock compressibility factor has the greatest influence on the oil generated overpressure，with a value of 99.056%，followed by the total organic carbon content， with a value of 0.342%. The influence of hydrocarbon generation factor and kerogen oil-generating conversion efficiency on the oil generated overpressure is 0.261% and 0.250%，respectively，and the porosity and formation pressure have a relatively small effect on the oil generated overpressure，which is 0.09% and 0.001%，respectively. The model also reveals that higher formation pressure is not conducive to oil generated overpressure，and higher formation pressure makes the oil generated overpressure smaller.