The invention discloses a small compressed air energy storage system and method and belongs to the compressed air energy storage technology. The small compressed air energy storage system is composed of a storage tank, an air compressor, a pressure expansion machine and an electric/generator part. The small compressed air energy storage system uses a dual-functional switch reluctance electric/generator as a core motor to replace independent compression motor and engine in a general compressed air energy storage system, the system cost can be lowered, the volume is reduced, and the system reliability is improved. In the air compression process, the electric rotating speed is regulated through a self-adaptive control method according to the compression characteristic of the air storage tank so as to obtain an optimized compression efficiency. In the process of releasing air to generate electricity, the air pressure is regulated through the self-adaptive control method so as to regulate the rotating speed of the generator and obtain the optimized power generation efficiency. The small compressed air energy storage system is reasonable in structure, small in volume, high in efficiency and capable of providing peak clipping and valley filling for an electrical power system, or the small compressed air energy storage system serves as a small renewable distributed power generation storage device.