Quantitative vulnerability analysis is still a challenge in landslide risk assessment. Comparing to fast moving slope failures, slow moving landslide poses risk to the buildings in long term damages, which are generally underestimated in risk assessment. To find out the relationship between the buildings vulnerability and the displacement of landslide, an inventory work was carried out on Tangjiao landslide, a large slow moving landside in the Three Gorges reservoir area, China. The ground cracks (location, length, width, distance to buildings, differential displacement) on the landslide were measured and 267 residential buildings (age, structure, number of floor and damage degree) on the landslide body were investigated. The most sensitive indicator for building vulnerability in slow moving landslide is crack width. The paper proposed a general formula for physical vulnerability which can be used in risk quantification.