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.