The invention discloses an air reservoir preparing and mounting tool which comprises a frame body, a fixed support, a brake cylinder, a main clamp and a tool rack, wherein the fixed support is arranged in the middle part of the upper part of the frame body, a right isolating seat is arranged on one side of the fixed support, and a left isolating frame is arranged on the other side of the fixed support; the brake cylinder is arranged in the left isolating frame in a sleeved mode, and a sleeve rod is transversely arranged in the middle part of one end of the left isolating frame; and brace rodsare longitudinally arranged at the two ends of the right isolating seat. The air reservoir preparing and mounting tool has the beneficial effects that the middle part of the other side of an air reservoir is tightly pushed and clamped for fixing by the main clamp, so that a worker can conveniently mount parts such as a valve, etc. on the side wall of the air reservoir, the worker can convenientlyoperate, and the worker can faster operate the air reservoir and mount the parts; a mounting tool for preparing and mounting the air reservoir is placed on a tool placement table at one end of the upper part of the tool, so that the space utilization and the object capacity of the tool are improved; and the tool is convenient in operation, is firm and durable, has good social benefits and is suitable for promotion and use.