When the Nanchang Metro Line 1 passes through the Ganjiang River, there is abundant groundwater with strong permeability, which makes it highly prone to sudden water and mud gushing accidents, affecting the tunneling of the shield tunnel. This paper obtains the appropriate slurry mix ratio and the soil pressure around the injection area through slurry fluidity and injection test. The results show that the fluidity of the synchronous injection material is affected by its initial injection pressure, and the pressure loss per unit length increases approximately linearly with the increase of the initial pressure. As the surface ratio increases, the pressure loss caused by friction and other factors during the slurry flow process becomes more significant. During the injection process, as the injection process progresses, the slurry consolidates in the soil, resulting in a decrease in its fluidity and thus affecting the pressure distribution of the injection system. In the Nanchang Metro Line 1 crossing the Ganjiang River project, the maximum surface settlement was 3mm. This study can provide a reference for similar projects.