Utilizing the selfmade unitbody model test apparatus, the deformation laws of backfill grouting were studied under different grouting pressures, different soil conditions and different ground water pressures. It was shown that high grout pressures can accelerate the consolidation rate of grout drainage and increase final deformation amount. And soil permeability coefficient was an important factor to grout deformation. The ground water pressure was more important for sand soil while the grout pressure was for clay soil. The proposed apparatus can truly reflect stress status of grout injected to tail void. And grout deformation properties were helpful to clarify the stratum stress release and stratum deformation of backfill grouting. 