A reversible dimmer device of gas discharge lamp and a control method for light adjusting thereof are proposed, in which a power switch on the wall or on an appliance is used to control actions of at least of a gas discharge lamp. When the power switch is turned on, a power signal is provided to drive the gas discharge lamp to produce a stable light source. The power switch is then fast pressed to make sure the times and timing of off-on switching so that a logic control circuit can output a logic control command. A frequency modulation control circuit is then used to adjust a power parameter according to the logic control command so that a variable frequency resonance drive circuit can vary the drive frequency of the power signal based on the power parameter. The gas discharge lamp can thus produce different luminance or different luminous effects.