The invention discloses a hydraulic power three-stage unfolding type coal bed gas cave manufacturing tool. The hydraulic power three-stage unfolding type coal bed gas cave manufacturing tool comprises an upper connector, a main shaft rotation system and a horizontal cave manufacturing system. The upper connector is connected with a drill pipe. The main shaft rotation system is provided with three jet flow holes and can be pushed to break rocks rotationally through the action force generated by hydraulic jetting. Meanwhile, the main shaft rotation system further comprises an auxiliary jet flow system arranged on the lower portion of the tool to assist the main shaft rotation system in breaking rocks rotationally. The horizontal cave manufacturing system comprises three stages of telescopic drill bits which can be unfolded stage by stage through hydraulic pressure. Each stage of drill bit is provided with three jet flow holes and is pushed to rotationally break rocks through the action force generated by hydraulic jetting. Rotation of the main shaft rotation system and the horizontal cave manufacturing system of the tool is pushed through hydraulic force, the rotation in the two directions cooperates with each other and forms a feedback mechanism, and therefore a cave is manufactured in a stage-by-stage unfolding mode laterally. The hydraulic power three-stage unfolding type coal bed gas cave manufacturing tool is easy and convenient to operate, easy to control, and capable of keeping stability of a well wall during cave manufacturing, preventing the well wall from collapsing and manufacturing the relatively regular cave. In addition, the hydraulic power three-stage unfolding type coal bed gas cave manufacturing tool can be applied to the expanding work of a necking down formation.