Based on grouting simulation experiments and numerical analyses, the formulations are established for predicting grouting amount, grout diffusion radius and compressive strength of stone body in the gravel soil; the proposed formulations are validated by indoor grouting experiments. Experimental results show that there are about 10%, 5% and 10% differences respectively between the theoretical values of grouting amount, grout diffusion radius and compressive strength of stone body and their actual measurement values; but these differences valuse are admitted. So, the formulation can be used to predict grouting amount, grout diffusion radius and compressive strength of stone body in actual grouting engineering of gravel soil. Therefore, the research results may not only provide theoretical supports for actual grouting engineering of gravel soil, but also provide technical references for disaster prevention and mitigation of landslide and debris flow induced in the gravel soil.