Double-sidewall diversion method is a common underground excavation method for large section shallow buried tunnels. Different excavation procedures and excavation penetration lengths have significant effect on the deformation of tunnel surrounding rock, and thus affect the overall stability of the tunnel. In order to consider the above factors, this paper, based on the Jiangjunshan Tunnel project of Zhuhai Black and White Surface, uses FLAC3D to establish a three-dimensional numerical model of formation structure, analyzes in detail the deformation laws of tunnel surrounding rock and lining under different excavation procedures and excavation penetration of the ultra-large section shallow buried tunnel. It further determines the applicability of different construction schemes. Optimize the construction scheme of double-sidewall diversion method for ultra-large section shallow buried tunnel. The results show that the larger the excavation footage length, the more significant the surrounding rock displacements and the lining deformation, while the smaller the excavation footage length will affect the construction efficiency and is not convenient for the mechanical operation. Upper and lower step excavation in different-side and same-side guide tunnels induces comparable tunnel deformation. The research results can provide a reference for double-side diversion construction of shallow buried tunnel with large section in bad geology.