The invention discloses a general constant-power electronic ballast for a high-intensity gas discharge lamp. The electronic ballast is characterized in that: the electronic ballast adopts a three-stage structure and consists of an active power factor correction (APFC) circuit, an average input current outer ring-based and peak current inner ring-based buck converter and a resonant full bridge inverter circuit; and 220V alternating current is filtered by EMI, the filtered alternating current is connected to the APFC circuit and converted into direct current, the direct current is converted into 0 to 150V adjustable direct current voltage by the buck converter, and the adjustable direct current voltage is converted into a frequency-adjustable alternating current square-wave voltage serving as an HID lamp driving signal by the resonant full bridge inverter circuit. The electronic ballast can obtain good constant-power characteristic and prolong the service life of an HID lamp, and can be matched with various HID lamps, including ceramic metal halide lamps, quartz metal halide lamps, high-voltage sodium lamps and the like.