The invention discloses a small-hole reinforced fracturing grain and single-surface hoop slit grain combined cutting undermine method, which comprises the following steps of: 1) drilling; 2) charging:enabling central cutting undermine holes to use a decked charge structure and the small-hole reinforced fracturing grain, filling a second-decked small-hole reinforced fracturing grain into the bottom of each central cutting undermine hole, then, immediately filling tap-hole clay of which the length is 400-500 mm, then, filling a first-decked small-hole reinforced fracturing grain, finally, blocking by the tap-hole clay, filling a second-stage single-surface hoop slit grain into wedge-shaped cutting undermine holes, blocking by the tap-hole clay, filling third-decked common explosive in auxiliary holes, blocking by the tap-hole clay, filling four-decked common explosive in caving holes, blocking by the tap-hole clay, filling five-decked common explosive in surrounding holes, and blockingby the tap-hole clay; and 3) blasting. According to the method disclosed by the invention, the volume of a cutting undermine cavity can be enlarged, a free surface is increased, a surrounding rock clamping function is lowered, and a blast hole use ratio and an explosive energy use ratio are improved.