A grouting method for bedrock under deep water conditions comprises the steps of positioning pier ships on water surface, wherein the two pier ships are arranged in parallel, anchored, positioned and fixedly connected, and a drilling rig is arranged between the two pier ships; an underwater casing pipe installation mode is applied between the water surface and an underwater bedrock surface, an underwater casing pipe is arranged between the water surface and the underwater bedrock surface, the lower end of the underwater casing pipe is inserted into the bedrock, the upper end of the underwater casing pipe is exposed above the water surface, and the underwater casing pipe is limited and fixed; an inner pipe and a dial indicator are arranged inside the underwater casing pipe; after the underwater casing pipe is installed and fixed, a drill rod and drill bit with a bore smaller than that of the underwater casing pipe are utilized in the underwater casing pipe, and conventional drilling is performed inside the underwater casing pipe through a core drill. According to the grouting method for the bedrock under the deep water conditions, construction difficulty of grouting curtain and consolidation grouting of bedrock under deep water conditions is solved, the effect that drilling and grouting of the bedrock under the deep water conditions are just like those of rock on land can be achieved, the construction is quick, simple, economic, reliable and safe, the operational needs of production can be met well, and good economic benefits are obtained.