in order to calculate the ground settlement caused by precipitation amount, the use of precipitation funnel precipitation area curve for saturated zone and the seepage zone, considering the change of moisture content of saturated zone caused by severe changes in the soil, in turn, led to its effective gravity stress change, consider the effect of seepage force and seepage area, based on calculating the stress changes in precipitation amount of compressed soil element, and through calculation of the random medium theory foundation pit surrounding soil settlement. Engineering practice shows that the calculated value is close to the measured value on the whole, the measured value is 15% higher, and the influence of precipitation is greater within 1.5 times of the excavation depth of the foundation pit. The research content can provide reference for estimating the ground settlement caused by foundation pit dewatering.