The soft surrounding rock of deep roadways is in the state of “micro-fracture and low permeability”. In order to solve the problem of grouting reinforcement of micro-fractures surrounding rock in deep roadways, the influence characteristics of auxiliary materials and additives on slurry flow were analyzed, and the composition and proportion of superfine cement-based composite grouting materials were determined: superfine cement accounted for 89.4%, superfine coal ash accounted for 5%, ultrafine mineral powder accounted for 5%, naphthalene water reducing agent accounted for 3~5‱, and lignin sulfonate calcium accounted for 1~3‱. The effects of water−cement ratio and water reducer content on slurry viscosity and water bleeding rate were tested by laboratory experiments. Based on the fracture characteristics of surrounding rock and the “Liu Jiacai Formula”, the influence law of fracture opening, grouting pressure and slurry viscosity on the slurry diffusion radius was analyzed. The results show that the slurry viscosity decreases with the increase of water−cement ratio and water reducer content, but the bleeding rate increases obviously with the increase of the two factors; when the water−cement ratio is 1.0 and the water reducer content is 3‱, the slurry has the advantages of “strong permeability, strong flow and low water bleeding rate”; the smaller the fracture opening is, the greater the required grouting pressure and the lower the required slurry viscosity. Aiming at the “micro-fracture zone” of surrounding rock in deep roadways, when the dynamic viscosity of the slurry is 2.0 mPa·s, the reasonable grouting pressure should be 12 MPa to meet the needs of grouting reinforcement engineering. The high-pressure grouting test of surrounding rock in the “micro-fracture zone” was successfully carried out by using the superfine cement-based composite grouting material.