Abstract: Granite weathered residual soil has special engineering characteristics. It will easily lead to the loss of strength, softening and disintegration of the soil body when exposed to water, causing geological disasters, and often bringing huge risks and economic losses to engineering construction. In this paper, combined with engineering examples, through theoretical calculations and comparative analysis of on-site monitoring results, the impact of dewatering and step-by-step excavation of foundation pits in the granite residual soil area is studied, and it is concluded that the depth of the water-stop curtain and the pre-embedded Conclusions such as slurry pipe, strengthening of precipitation management and timely back cover have certain guiding significance for the construction of Guangzhou Metro, and also provide references for the construction of subway foundation pits under similar conditions in other cities.