In this paper, the causes of leakage to the foundation pit is illustrated in detail by the example of a construction site in Wenzhou City, where drainage and plugging technology was used to treat leakage to the foundation pit. A diversion pipe was used to drain the leakage outlets to relieve the water pressure in the soil layer of the leakage site and some surrounding areas, and to improve the success rate of leakage stoppage. Then, double liquid grouting was used to cut off part of the water flow path so as to reduce the water flow from the leakage outlets; and to reinforce the foundation pit. The results showed that drainage and plugging provided efficiency, accuracy and effectiveness in the field, with 57 leakage points in the foundation pit effectively treated.