Grouting mortar has widespread application in engineering because of the advantages of good durability, low cost, and environmental friendliness. To study the flowing properties of grouting mortar, laboratory minislump tests taking different rheological parameters of grouting mortar into consideration were conducted to obtain the flow time and flow pattern of grouting mortar. A modified MPS method (moving-particle semi-implicit method) introduced two sections of Bingham rheological, and segregation was proposed. The effects of the plastic viscosity on the flow state of mortar were studied, and the relationship between the plastic viscosity and the flowing time was established. The numerical results show that the modified MPS method can be used to predict the flow time and flow pattern of mortar in the template, and plastic viscosity has a great influence on the flow time of concrete, and with the increase of plastic viscosity, the time to flow to the specified area also increases. Moreover, the analysis of the rheological parameters can provide the basis for the design of mix ratio in the construction practice.