The invention discloses a method of fracturing a coal-bed gas reservoir and belongs to the field of coal-bed gas exploitation. The method comprises following steps: after perforation in a middle-upper part of the coal bed and a coal bed top board above the coal bed, active water fracturing fluid is pumped and injected in the coal bed top board to form a first crack; low sand ratio sand-carrying fluid and high sand ratio sand-carrying fluid are successively pumped and injected into the first crack, and a second crack communicated with the first crack is formed in the coal bed, and the extension of the second crack is promoted to form multiple branchlike cracks containing sand support agent. The low sand ratio sand-carrying fluid comprises following components by percentage of mass: 0.1-0.3% carboxymethyl hydroxypropyl guanidine gum, 1-2% KCl, 0.5-1% discharge aiding agent, 8-12% sand support agent, and water as balance; the high sand ratio sand-carrying fluid comprises following components by percentage of mass: 0.1-0.3% carboxymethyl hydroxypropyl guanidine gum, 1-2% KCl, 0.5-1% discharge aiding agent, 12-48% sand support agent, and water as balance. The method provided by the invention can form a long distance supporting seam network in the coal-bed gas reservoir, and effectively improve the yield of the coal-bed gas reservoir.