The energy storage technology is playing an important role in improving power grid stability. Aiming to the randomness and intermittent characteristics of wind power generation, the paper proposed a scheme of mechanical elastic storage energy and power generation system based on flat spiral spring. The flat spiral spring, which is the core component in the system, is selected as the research object, and the mechanical model and the finite element model is created. The geometric parameters of spring are determined. The maximum deformation and the stress distribution of spring are obtained. Moreover, the modal analysis of spring is carried out and the natural frequencies and modes of vibration of first 20 orders are obtained. The relationship between the natural frequency and deformation is also analyzed. All the results in this paper provide a strong basis for the optimization design of spring and the calculation of energy density.