Abstract: The effects of acid rain on mechanical properties of the shale in the slip zone of Jiweishan landslide in Wulong of Chongqing are investigated in this article. Shale samples were taken from the extending downstream of the slip zone of the Jiweishan rock avalanche, and were made into powder and block before immersed in the solution. In laboratory, calcareous shale in the slip zone of the Jiweishan landslide was subjected to acid water immersion where pH is 3, and was tested for changes in their compositions. The experimental results show that the calcareous exsolution was observed in the acid solution with shale immersed, and the velocity of the shale powder was faster. The ion components of the water from the toe of the Jiweishan landslide were tested, and the results show that Ca2+ concentration was obviously higher than that of the acid rain, indicating that the calcareous exsolution was faster under the circumstance with acid rain. The exsolution of calcite from the calcareous shale may lead to the decrease in the strength of the slip zone.