The sandycobble stratum has many characteristics such as small cohesive force, large internal friction angle, large permeability coefficient and poor fluidity and stability, which would easily cause the collapse and gushing of the face when earth pressure balance shield tunneling in. Hence, a polymeric foam agent PSA is developed for the waterrich sandycobble stratum, and it is applied to shield tunneling. The applicable results show that the soil conditioning effect of the polymeric foam agent PSA in fullsection waterrich sandycobble stratum is just as good as that of imported ones and better than that of domestic foam agents, and can fully meets the soil conditioning requirements of the shield tunneling in fullsection sandycobble stratum. By adopting polymeric foam agent PSA, about 9.5% of the material consumption per ring can be saved, which shows obvious economic benefits and popularizing value.