The invention relates to a soil modifier for earth pressure balance shield. The soil modifier is a foaming agent mixed from a foaming agent, a foam stabilizing agent and water. The foaming agent comprises of sodium alkyl sulfate, alkylbenzene sulfonate, alpha-alkenyl sodium sulfonate and fatty alcohol-polyoxyethylene ether. Each group is in the following weight percentage: 1-13% of sodium alkyl sulfate, 0.3-18% of alkylbenzene sulfonate, 0.5-15% of alpha-alkenyl sodium sulfonate, 0.5-3% of fatty alcohol-polyoxyethylene ether, 0.1-2% of foam stabilizing agent and the balance of water. The soil modifier can be used for earth pressure balance shield construction, has good stabilizing effect on excavation faces of different geological structures. Compared with other foaming agents, the soil modifier has higher foaming expansion rate and better stability, and can better improve the plastic flow property and permeability of soil body.