Abstract: In order to accurately and quantitatively evaluate the vertical sealability of the fault, this paper, taking the Binhai-Gangxi fault in the Qikou Sag as an example, makes full use of relevant data such as drilling, logging, and 3D seismic as the basis to establish a lateral plugging coefficient of the geological model, calculate the lateral fault-reservoir displacement pressure difference of the fault, and couple the lateral plugging ability of drilling around the fault with the mudstone smearing method that characterizes the vertical plugging.It is calculated that the critical mudstone smear coefficient value of the fault is 6.2.Based on this quantitative evaluation, the vertical sealability of the Upper Paleozoic strata of the Binhai-Gangxi fault is obtained and verified.The results show that the upper Paleozoic of the Binhai-Gangxi fault has good vertical plugging properties as a whole, but the northwest section and the middle section have poor vertical plugging properties.The research results provide guidance and reference for oil and gas exploration in research area with complex structure background.