Burst is one of the main disasters in the foundation pit engineering. However, the current methods for analyzing burst stability of the foundation pit on confined water could not reflect the failure mechanism. According to mechanism of hydro-fracturing, the seepage-stress coupling should be considered when burst is studied. The coupling model for the foundation pit burst in hydro-fracturing process is established based on Biot's consolidation theory, and the dynamic evolution of soils permeability and mechanical characteristic are considered. The possibility of burst is explored by analyzing the change of stress field and seepage field during the excavation process. The results show that burst begins in tension failure in aquiclude of foundation base, whilst the periphery of foundation base is where more likely burst occurs;hydro-fracturing caused by water wedge effect of weak surface infiltration (it is the initial tension crack) provides the channel for burst and a confined bed with high pore water pressure is the precondition for burst, but high hydraulic gradient is the root cause for burst.