Abstract: The region of Zhouqu and Wudu in Gansu province is one of the most intensive activities and the most frequent areas of geological disasters such as landslide and debris flow. The process of the water-rock interaction of the wide outcrop of Silurian slate in the area is one of the main reasons that the landslides and debris flow can highly develop. The paper observes the macro morphology and tests the variation of qualities in elastic wave velocity and uniaxial compressive strength of the slate samples after saturated cycles and wet and dry cycles in different times. It compares the process of crack propagations and the variations of quality, strength and such related indicators of slate sample under two kinds of water-rock interactions. The test results reveal the degradation law of slate under water-rock interaction. Preliminary discussions are given on the mechanism of degradation of slate under different water-rock interactions. The study provides a useful reference for evaluation and prevention of landslide and debris flow disasters.