The invention provides an efficient grooving construction method for an underground diaphragm wall in micro-weathered granite. The method specifically comprises the following steps: 1, geologically surveying the construction site; 2, determining the rock breaking method; 3, determining blasting parameters; 4, drilling holes from a sand layer to the surface of a rock layer, and unearthing; 5, distinguishing a rock sample, and then determining and drilling to reach intermediately-weathered granite; 5, feeding a PVC (Polyvinyl Chloride) pipe for protecting a blasting lead; 7, drilling hole in the rock layer until reaching depth 1m more than the design burial depth; 8, feeding explosive and blasting. With the adoption of the efficient grooving construction method for the underground diaphragm wall in the micro-weathered granite, the defects and shortcomings like difficult construction in the micro-weathered granite or slow construction progress, and poor grooving quality of the existing construction method of covering sand the micro-weathered granite can be overcome; the efficient, high-precision and deep-rock-embedding grooving construction in the micro-weathered granite is realized; the method has a good effect and fast to groove.