The invention discloses agoaf grouting method based on pinnate horizontal branch directional drilling technology. The goaf grouting method based on pinnate horizontal branch directional drilling technology comprises the following steps thatstep 1, drilling is arranged, specifically,pinnate horizontal branch directional drilling is designed in a treatment area of a fully mechanized goaf, a verticalsection, a deflecting section, and afissure zone horizontal extension section; step 2, a grouting material is determined, and the grouting material consists of cement, flyash or clay, and an accelerator; step 3, drilling and grouting operations of each directional drilling are conducted, a drill tool is first lowered and drills into the vertical section and the deflecting section, and a forward drilling grouting ishorizontally conducted.Thus, according to the goaf grouting method based on pinnate horizontal branch directional drilling technology,disadvantages of vertical drilling technology in fully mechanized working face goaf grouting technology are overcome, the pinnate horizontal branch directional drilling is constructed from the earth surface to the lower middle layer of the fissurezone, grout is filled and strengthening is conducted on goaf caving zone rock mass, underground residual cavities, and fissures, activation space of an old goafis thoroughly eliminated, and thegoaf treatment is more effective.