The invention discloses a multifunctional and adjustable support dismantling method and device. The dismantling device mainly comprises a rotating control device and an abrasive jet cutting device, wherein the rotating control device comprises stable supporting seats, connecting bearings, an adjustable rotating disc and sliding bearings; the abrasive jet cutting device comprises a control module, a water delivery pipe, a high pressure water pump, an abrasive material tank, sealing rings, oscillating nozzles, electromagnetic valves, distance measuring instruments and sealing soft belts; the implementation process comprises the following steps: arranging the supporting seats on the periphery of a support, assembling the appropriate rotating disc according to the diameter of the support, regulating the soft belts, mounting the cutting device on the rotating disc, performing real-time distance measurement by using the distance measuring instruments and feeding back the parameters to the control module, enabling a water source to be connected, opening the electromagnetic valves through the control module according to the feedback information, performing rotary cutting, stopping cutting when detecting that the support is about to be cut off, removing the device, and dismantling the support by using a simple physical means. Compared with the conventional method and device, the multifunctional and adjustable support dismantling device and method has the benefits of being flexible in structure, convenient and efficient, and safe and controllable.