The tunnels may traverse soft soil strata rich in hazardous gases such as methane, which poses several adverse effects on construction. These effects primarily include excessive deformation of the tunnel, leakage, or migration of hazardous gases causing soil deformation and settlement, thereby negatively impacting shield tunneling operations; and the ingress of hazardous gases into the tunnel, which could lead to fires or explosions upon encountering an ignition source, as well as endangering the health of construction personnel within the tunnel. Therefore, this paper focuses on the critical technical issues associated with the construction of the B Line tunnel in the presence of hazardous gases. Utilizing numerical simulations, the uneven settlement and reinforcement techniques are analyzed for shield tunneling through hazardous gas-bearing strata. Based on a comprehensive geological investigation report, a robust finite element model of the tunnel has been developed. The implementation of reinforcement measures and strata stabilization techniques has proven effective under identical leakage conditions. The maximum displacement of the tunnel strata was reduced from the initial 2.0–1.5 mm, resulting in a 25% decrease in overall strata displacement. The findings will provide scientific basis and technical support for similar construction projects.