Provided is a smart power-saving system of a traffic information electronic display board, which adjusts the brightness of the electronic display board according to a signal of a passing vehicle detected by an operation detection sensor such as a radar sensor, to maintain power-saving brightness at a minimum power when there is no passing vehicle, and to display, when a passing vehicle is detected, normal brightness up until the passing vehicle has passed the electronic display board, and then automatically return to the power-saving brightness, thereby reducing the power consumption of the electronic display board during times when there are no passing vehicles.