Abstract: The shield machine planetary gearbox is an essential component of the shield machine drive system and serves as the main transmission device in the excavation system, connecting the cutterhead to the hydraulic motor. This paper presents a comprehensive calculation and analysis of the strength and gear modification for the designed shield machine planetary gearbox. Specifically, fatigue and static strength verification of gear and bearing parameters were performed using MASTA transmission analysis software, and a micro-geometry gear modification optimization scheme was proposed under different working conditions. Meanwhile, the strength of the main structural components was evaluated using ABAQUS finite element analysis software. The results indicate that the designed gearbox parameters and structure meet the intended design requirements.