Research results: Based on the summary on influence of understructure work construction on ground water environmental and taking the Line 2 of Xi ˊan City Rail Communication as an example , the influence of foundation pit precipitation in construction period on the groundwater environment is calculated with empirical formula and the influence on the flow field of groundwater after metro operation is predicated with the numerical simulation the method. However, the foundation pit precipitation only occurred in the Zhang Village station with the central water level dropping 6. 3 m, the precipitation of 10 454. 15 m3/d and influencing radius of 441 m. This will have certain influence on the ground-water flow because the underwater flow mute will be dammed by the metro track, resulting in head water raising and rear water lowering with simulation change amplitude of underground water level between 0～1.7 m.