The invention relates to reinforcing slurry for a semi-rigid base and a grouting method of the reinforcing slurry. The reinforcing slurry comprises the raw materials by mass percent: 95-99.7% of cement, 0.06-1.0% of water reducer, 0.1-0.3% of retarder, 0.03-0.07% of coagulant, 0.02-0.04% of plastic expanding agent, and 0-4.79% of mineral filler, and the reinforcing slurry is prepared through stirring the raw materials. The grouting method comprises the steps of locating hole sites at 0.25-meter positions of the periphery of a crack in the pitch, and drilling down at the hole sites to the top of a roadbed, wherein the distance between every two holes is 0.75-1.0m; adding water into a stirrer, then adding the slurry, wherein the mass ratio of water to slurry is less than or equal to 0.35, the stirring speed is greater than or equal to 500r / min, and the stirring time is less than or equal to 5 minutes; grouting into a grouting pipe, wherein the grouting pressure is 0.5-1.0MPa, and the time for stirring and grouting is less than or equal to 30 minutes; and after grouting, sealing the grouting holes with sealant or pitch. The reinforcing slurry has the characteristics of low cost, good fluidity, fast speed in condensation and high strength, and the grouting method is simple.