This paper presents a case study of curtain grouting to prevent water and mud inrush disasters for a weathered granite tunnel in Guangxi, China. First, the basic information of the Junchang tunnel is given, including ground conditions, water and mud inrush disasters, and the subsequent prevention countermeasures. Then, we present the original grouting design and procedure, and the field operation of 25 grouting cycles and excavations for the evaluation of the grouting effect and suggestion for future grouting work. Based on the field investigation, the values of the major grouting parameters are suggested, including grouting thickness of 5– 8 m, grouting length of 15– 18 m (3– 3.6 times of thickness), and per-meter grouting volume of 34.2 m³. Furthermore, the guidelines for composite materials selection are proposed for the various flowing water environments. Moreover, the space positions and water quality of the inspection boreholes and the original water richness of the ground should be taken into consideration in the grouting evaluation criteria. The optimized grouting parameters, materials selection and evaluation criteria provide important references for disasters prevention in similar projects.