A method of controlling a ballast for a high intensity discharge (HID) lamp and related system. The method includes setting initial operating parameters of the ballast to turn on the HID lamp, generating starting transient electric characteristic values of the HID lamp by measuring actual electric parameters at a predetermined time during a transient process after the HID lamp is turned on, searching stored data for a rated power corresponding to the starting transient electric characteristic value range of the HID lamp after determining that the starting transient electric characteristic value is within stored starting transient electric characteristic value ranges of the HID lamp, and searching the stored data for a corresponding ballast operating parameter, to allow the HID lamp to operate in the corresponding rated power, and realize that a single ballast can be adapted to and control the HID lamps to operable in their respective specific rated power.