Taking XidanLingjing Hutong crossover tunnel on line 4 of Beijing Metro as example, the author, by means of theoretical analysis and numerical simulation, studies on the advance reinforcement mechanism of grouted roof pipes, the scope of the plasticized zones of the ground, the maximum ground surface settlement values and the comparison of the settlement under different reinforcement modes in the construction of largespan tunnels located in fine silt sand ground. The construction practice confirms that the study has achieved good results.