Abstract: In order to ensure the safety of the adjacent construction of the super-large rectangular pipe jacking shield tunnel in the soft ground, taking a rectangular pipe jacking shield tunnel adjacently passing under the existing high-speed railway as a study case, the effects of different construction and reinforcement schemes of the superlarge rectangular pipe jacking shield tunnel adjacent to the high-speed railway section are studied. The results show that when advanced grouting is adopted, the active instability displacement can be reduced by 25.64%, the passive instability displacement can be reduced by 17.65%, and the track settlement can be reduced by 30.38% for the excavation face. And when the manually excavated pile + D-shaped steel auxiliary beam are adopted, the active instability displacement can be reduced by 51.28%, the passive instability displacement can be reduced by 29.41%, and the track settlement can be reduced by 42.31% for the excavation face. Field monitoring shows that the maximum settlement of the track after reinforcement by the manually excavated pile + D-shaped steel auxiliary beam is only 1.65 mm. The super-large rectangular pipe jacking shield tunnel has successfully passed under the existing highspeed railway. The manually excavated pile + D-shaped steel auxiliary beam ensure the adjacent construction safety of the super-large rectangular pipe jacking shield tunnel and the normal operation of the high-speed railway.