The foam is usually used to carry out ground conditioning. The ground conditioning will affect shield boring performance directly, and it is the key to tunnel face stability, shield boring efficiency and wear of cutting tools. The ground conditioning effect of shield boring in composite strata of Humen Shangmaocheng StationChang’an Xiabian Station on GuangzhouDongguanShenzhen intercity railway is studied. The numerical models for cutterhead torque and boring parameters of shield boring in composite strata are established. The influence of foam on cutterhead torque is analyzed; and then the boring parameters are optimized. The analytical results show that the cutterhead torque can reach the optimal value (2 033.1 kN·m) when the volume of foam reaches 0.01 m3 and the volume fraction of foam reaches 7%.