易损性反映了特定社会的人们及其所拥有的财产对自然灾害的承受能力，不同地区的不同承灾体在不同时间里对不同的灾害有不同的易损性特征。通过选取定性评价因子，对易损性进行等级划分，从而做到定性分析；通过对承灾体、时空概率和易损性调查，由引入的易损性指数可以对易损性做到定量分析。最后还提出了易损性的等级划分标准。结论表明：易损性指数是表示各因子在易损性判别中作用大小或强弱的物理量，是一个相对比较的数值，是定性分析的定量表示。

The ranks of geo-hazard vulnerability were firstly determined and qualitative analysis was made by selecting qualitative assessment factors. Based on surveys of the disaster-affected body, the spatio-temporal probability and the vulnerability, the authors calculated the vulnerability and proposed a grading standard. An accumulation landslide in the Qinling-Bashan mountain area was taken as a case study. It is concluded that vulnerability index is a physical quantity that indicates the effect degree of each factor on the vulnerability assessment. It is the quantitative expression of qualitative analysis.