Fuzzy mathematics is an important means to quantitatively evaluate the properties of fault sealing in petroleum reservoirs. To accurately study fault sealing, the comprehensive quantitative evaluation method of fuzzy mathematics is improved based on a previous study. First, the single-factor membership degree is determined using the dynamic clustering method, then a single-factor evaluation matrix is constructed using a continuous grading function, and finally, the probability distribution of the evaluation grade in a fuzzy evaluation matrix is analyzed. In this study, taking the F1 fault located in the northeastern Chepaizi Bulge as an example, the sealing properties of faults in different strata are quantitatively evaluated using both an improved and an un-improved comprehensive fuzzy mathematics quantitative evaluation method. Based on current oil and gas distribution, it is found that our evaluation results before and after improvement are significantly different. For faults in ''best'' and ''poorest'' intervals, our evaluation results are consistent with oil and gas distribution. However, for the faults in ''good'' or ''poor'' intervals, our evaluation is not completely consistent with oil and gas distribution. The improved evaluation results reflect the overall and local sealing properties of target zones and embody the nonuniformity of fault sealing, indicating the improved method is more suitable for evaluating fault sealing under complicated conditions