Abstract: This paper addresses the issue of uncertainty in the grading of geological hazard susceptibility evaluation factors and introduces the adaptive expansion factor fuzzy coverage grading method (AIFFC) to optimize the grading of geological hazard susceptibility evaluation factors. Taking Xiangxiang City, Hunan Province as the research area, nine evaluation factors, including slope, slope direction, elevation and average annual rainfall, normalized difference vegetation index for land use, roads, faults, lithology, were extracted. The AIFFC method and the natural breakpoint method were used to grade continuous factors. These graded factors were then incorporated into a weighted information model and random forest model to obtain a susceptibility zoning map for the study area. The superiority of the AIFFC classification method was tested through the comparison of single-factor grading results, disaster product ratio analysis,and ROC curve comparison of susceptibility zoning results. Based on AIFFC, the hazard accumulation ratio of the random forest model and the weighted information entropy model in the high susceptibility areas increased by 56.3% and 74.6%, respectively, while in the low susceptibility areas, it decreased by 48% and 58.1%, respectively. The AUC values increased by 7.6% and 2.7%, respectively. The AIFFC classification method is used to optimize the evaluation factor classification of geological disaster susceptibility, which significantly improves the rationality of the evaluation of geological disaster susceptibility.