The invention relates to a machining tool of an inclined hole in an inner cavity of a wind power wheel hub and a machining method of the machining tool. The machining tool comprises a working platform, a cylindrical support, a long-strip support and a hole drilling template, wherein three sector-shaped blocks are uniformly distributed around the center of the upper part of the working platform; a round seam allowance is determined by the sector-shaped blocks and is positioned at a wheel hub arrangement center in a manner of being in clearance fit with a wheel hub main shaft; the cylindrical support and the working platform are concentric; the other end of the long-strip support is a wedge-shaped surface and is in sliding fit with the hole drilling template; and the hole drilling template is provided with a positioning hole. The method comprises the following steps: 1, matching a positioning block with a thread hole, which aligns to a part to be machined, in one circle of thread holes in a wheel hub axial plane flange; 2, embedding one end of the long-strip support into any one square groove in the upper end of the cylindrical support, and fixing through a bolt; and 3, rotating for 120 degrees, and machining the next part in the other square groove mounted in the upper end of the cylindrical support. The machining tool and the machining method, provided by the invention, have the beneficial effects that the operation is simple, the cost is low, the quality of products is guaranteed, the machining efficiency is improved, and the cost and risks are reduced.