The invention discloses a control device for improving the frequency stability of a double-area interconnected power system. A battery energy storage unit, a normally open relay, a normally closed relay, a buck chopping circuit, a boost chopping circuit, a terminal capacitor, a converter and a power smoothing device are connected with one another so as to form the control device; the device is arranged in two power system areas; and the power output ends of the two areas are connected with each other. The invention also discloses a control method of the control device for improving the frequency stability of the double-area interconnected power system. An intelligent PI controller is adopted to maintain the dynamic balance of the output power of the interconnected double-area power system; and therefore, fluctuant and intermittent wind power resources can be fully utilized, the dynamic balance of the interconnected double-area power system can be maintained, the frequency of the double-area interconnected power system can be stable, and the reliable operation of the interconnected power system can be ensured.