In order to enhance tensile strength and crack resistance of grouting materials in earthen sites, use coir fiber mixed glutinous rice pulp, calcined ginger nuts and soil modified grouting materials as the research object, explore the law of influence on grouting materials in mobility, shrinkage, compressive strength and flexural strength about fiber content and length. The test results indicate that the higher the coir fiber content and length is, the lower the slurry mobility is, while there was no significant correlation between fiber length and shrinkage rate. The good bridging ability of coir fiber can effectively improve the compressive strength, flexural strength and ductility of the solidified slurry, and the coir fiber content and length have the optimal values. It is recommended that the reinforcement ratio should be 6mm in length and 0.5%~0.6% in content, so the compressive strength and flexural strength can be increased by 49.09% and 32.08% respectively. However, excessive and long coir fibers are prone to bending and agglomeration, which will lead to a substantial reduction in fluidity and mechanical strength.