Abstract: Landslide dam has typical spatial variation characteristics that the composition is disordered, the particle sorting is significant, and the spatial structure is complex, which is easy to form dam-break flood disaster under the erosion of water flow. How to quantitatively study the spatial distribution characteristics of parameters such as void ratio and gradation of landslide dam is a fundamental problem to be solved urgently. In the physical model test, Structure-from-Motion (SfM) of the three-dimensional reverse reconstruction technology is introduced, and the discrete block sampling method is integrated simultaneously. A complete methodology that includes orderly discrete block design, image acquisition and quantitative analysis of material spatial variation characteristic field is proposed for landslide dam. Subsequently, experimental validation and application are carried out based on this methodology. The test results show that both particle size distribution and void ratio demonstrate a significant variability under the condition of three-dimensional space for landslide dam materials. The proposed methodology endows the spatial location information attribute composed of void ratio and gradation, which greatly solves the problem of lack of data support for the spatial distribution characteristics of landslide barrier materials, and lays a data foundation and method approach for quantifying the accumulation form and spatial variability of wide-graded barrier.