The invention discloses a cascaded static var generator and a control method thereof. The cascaded static var generator comprises three phases of bridge arms with same structure; each phase of bridge arm is formed by connecting at least one stage to N(th) stages of multi-element energy storage power units in series; each multi-element energy storage power unit is formed by connecting a multi-element energy storage power module, a bidirectional controlled rectification circuit and an H-bridge inversion power module; and output ends of the H-bridge inversion circuits in each stage of multi-element energy storage power unit are cascaded to achieve high-voltage output. After the multi-element energy storage power units are integrated, active and reactive power control of a device can be simultaneously achieved; various energy storage elements such as a supercapacitor and a storage battery can be accessed; frequent power fluctuation in a system can be relieved, and the function of peak load shaving can be achieved; the numbers of the energy storage units connected in series can be substantially reduced, and the requirement for component parameter consistency is reduced; meanwhile, optimal charging and discharging control on each energy storage component is achieved; and moreover, expansion is promoted so as to increase system capacity.