In order to ensure the structural safety and force transfer during the excavation of the connection passage for superlarge-diameter shield tunnel, a comparative design of internal reinforcement measures was conducted. Based on the Hangzhou Zhijiang Road water conveyance gallery and road elevation project, a numerical model of solid discrete segments was established using a load-structure pattern. The influence of joint bolts and embedded steel bars on the stress distribution in the tunnel opening space was considered. The accuracy of the calculation method was verified through full-scale tests. The mechanical characteristics of the tunnel structure after segment opening and the range of opening influence were studied using an elastic-plastic analysis method. The reinforcement effects of different types of temporary steel supports and frames were analyzed. The results show that after the segment is opened, the concrete tensile stress near the bolt holes tends to concentrate due to the incompleteness of the structure, leading to failure. The range of influence on adjacent intact segments is approximately within three rings around the opening ring. For the cross passage with a large opening excavated in the vehicle lane of a superlarge-diameter shield tunnel, using a single steel support reinforcement method still results in significant deformation of the segment structure. Based on the temporary steel support, with the combination of the temporary steel frame, the tunnel is reinforced in a composite way. This effectively alleviates the sudden increase in internal force of the intact ring adjacent to the opening ring, thus ensuring the safety and stability of the tunnel structure after the expansion excavation opening.