For a landslide made up of soil-rock mixture near the dam of a large hydropower station in southwest China, in-situ infiltration tests were carried out by using improved double-ring infiltrometer. Four points at different places in the sliding body and six points in the sliding zone were tested respectively. The research indicated that the infiltration rate of soil-rock mixture was quite large and was close to that of non-cohesive coarse-grained soil. Meanwhile, the average infiltration rate in sliding body was 3-4 times larger than that in the slide zone. Indoor granulometric test on the soil of sliding body and sliding zone indicated that the content, density, particle shape and source of soil with diameter less than 5 mm are the main causes of infiltration rate difference.