Taking the deep foundation pit of Water rich round gravel layer in the enclosure area of Nanning Metro No.4 Nahong Interchange Station as an engineering example, based on the monitoring of the horizontal displacement of the pile item, the horizontal displacement of the pile body, the surface settlement outside the pit and the ground water level, the deformation law and mechanism of the retaining structure with double-row piles are analyzed, at the same time, the effect of water stop curtain is evaluated. The results show that the horizontal displacement of pile top increases rapidly in the early stage due to the excavation of foundation pit and the properties of round gravel soil, and the deformation of the pile body during the stop period shows a certain time effect due to the rheological properties of Mudstone, and the horizontal displacement curve of pile body is “bulging” , the maximum value of double-row piles is only 23.22 mm, there is almost no displacement at the bottom of the pile, and the stability of the pile is good, the maximum value is only 0.12% H, and the influence of excavation on the surrounding surface is mainly in the range of 0.7 H. Compared with the monitoring initial water level, the lowest point of the groundwater level outside the pit is 950 mm, which indicates that the high-pressure rotary jet grouting pile has a good water stop effect. It is feasible to adopt the double-row pile supporting structure in the round gravel layer, and the high-pressure rotary jet grouting pile waterproof curtain can meet the construction requirements.