The characteristics of low permeability and low natural productivity of tight oil reservoirs determine that large-scale hydraulic fracturing is often used to improve reservoir permeability, initial production and ultimate recovery. The reservoir permeability after fracturing is an important parameter to evaluate the hydraulic fracturing effect and single well productivity. At present, the research on the theoretical calculation model of tight oil reservoir permeability after fracturing considering the influence of multiple factors is still insufficient. Most use experimental measurement or well test measurement, which are costly and complicated to operate. Therefore, based on the principle of pressure drop well test, according to the fracturing operation curve, and considering the comprehensive effects of fracturing fluid loss and fracture propagation, this paper established a mathematical model for predicting the permeability after fracturing in tight oil reservoirs, which can directly calculate the permeability after fracturing by using fracturing operation data. Because the mathematical model is more complex, Matlab software is used to solve the problem through the difference dispersion iteration. Based on the actual fracturing data in an onshore area, the calculation and analysis show that the calculated permeability after fracturing is close to the interpreted permeability of well test. But the well test permeability is the effective permeability of the reservoir, which shows that the calculation result of this model is believable. The further analysis shows that the principle of this model is the same as that of the well test, but the difference is that the well test interpretation software can not calculate the permeability of tight oil reservoir after fracturing considering the comprehensive influence of fracturing fluid leakage and fracture propagation, moreover, the well test interpretation software requires parameters to be obtained from the well test admission data, while the calculation model in this paper only needs to record the fracturing operation data during the fracturing process. It can save well test operation time and cost, which can save the time and cost of well test operation. The calculated results will provide a reference for the evaluation of fracturing effect and productivity prediction of tight oil reservoir after fracturing.