A major concern in underground infrastructures is how to sufficiently seal the area from water ingress. To achieve this, grout needs to be spread adequately in the surrounding fractures. Cement-based composite grouting is probably the best method for this purpose because of its lower costs and reduced environmental impacts. Chemical reaction accompanied by the flow is a prominent feature of cement-based composites. Rheological properties, especially yield stress and viscosity, are non-uniformly distributed in time and space. In this paper, the rheological properties of quick-setting slurry of cement-based composites were measured over time, and the rheology constitutive equation including time was established based on non-Newtonian fluids. Considering the rheological properties, the Lagrangian method was introduced to track their space–time distribution, and then a dynamic model of quick-setting slurry was established based on continuity equation and momentum equation. The relationship between time-varying rheological characteristics and flow field characteristics was obtained through a numerical simulation of equal pressure injection and equal flux injection. The simulation results were compared with the experimental results in the references, thereby verifying the reliability and accuracy of the model. Results show that the local erosion state and local sealing effect of grouting directly depend on the yield stress of different positions in the flow field. The yield stress of quick-setting slurry increases rapidly with time, which is more likely to affect the flow field, and the viscosity of the slurry has a small effect on the flow field.