Abstract: Based on the underground project attached to the station of Suzhou Rail Transit Line 5, the stability of driving face of the rectangular pipe jacking was investigated. The silo and wedge model was modified, and the effective support pressure was derived based on the limit equilibrium theory. The maximum support pressure was obtained by optimization method, and the parameter analysis was carried out. The results show that the support pressure is decreased with the increasing of soil strength parameter, and it is increased with the increasing of tunnel geometry parameter.The support pressure result obtained by the optimized wedge model is greater than that by the traditional silo model, which is conducive to avoiding construction risks. The actual support pressure（71.00-90.00 kPa） is greater than the theoretical calculation result of 51.36 kPa, which indicates that the support pressure is suitable. The surface collapse or large settlement is presumed to be construction failure or insufficient support force due to unfavorable stratum conditions.