The invention is a plant crusher with a spiral fly cutter drum, which is used for cutting and crushing large timber, templates, tree roots, and straw plant raw materials. The main body is a plant crusher, and the cutter drum part of the plant crusher is a spiral fly cutter drum; the spiral fly cutter drum comprises a cutter drum and fly cutters distributed on the surface of the cutter drum, wherein the fly cutters or fly cutter edges orderly arranged along an extension direction of a central axis of a cutter drum are arranged in a spiral manner. The plant crusher can not only cut rigid, soft, and small wastes, but also perform primary crushing formation of large wastes, templates, and tree roots; the plant crusher can not only realize the processing of soft and rigid small materials, but also perform cutting of large wastes, templates, and tree roots; no other procedures are required, such as feeding and processing after large timber is splitted into small timber by a wood-splitting machine, which saves a lot of time and cost.