Abstract Grouting material is the core force transfer medium of grouting sealing and anchorage reinforcement methods for cracks in earthen sites; the performance of grouting slurry is the key to affecting the reinforcement effect. To solve the problems of poor flexural strength, easy shrinkage and cracking of existing grouting slurry, using Glutinous Rice Pulp, Calcined Ginger Nuts, and Loess Soil as substrates, and choosing the content and length of basalt fiber (BF) as control variables, 13 groups of specimens were designed by orthogonal test method to explore the influence of mixed fiber on the mobility, shrinkage, compressive, and flexural strength. The microstructure was analyzed by SEM to explain the strengthening mechanism from physical and chemical perspectives. The results show that the mobility decreases linearly with the increase in BF content and length; after mixing BF, the shrinkage rate is significantly reduced, but when the fiber length and content are relatively high, the surface is prone to cracking. The excellent bridging ability of BF can effectively improve the compressive and flexural strength of the specimen. When the fiber length and content are high, the specimen shows certain ductile failure characteristics, and the fracture energy increases more than 10 times.