An automatic brake assist device for an electric two-wheeled vehicle, the electric two-wheeled vehicle includes a main control module, having: a radar sensor module, used to measure a distance from a pair of objects; a control module, connected to the radar sensor module and the main control module, when the distance is changed from greater than a first braking distance to less than the first braking distance, transmitting a first brake braking mode signal to the main control module to decelerate the electric two-wheeled vehicle; when the distance is changed from greater than a second braking distance to less than the second braking distance, transmitting a second brake braking mode signal to the main control module to decelerate the electric two-wheeled vehicle; when the distance is changed from greater than a third braking distance to less than the third braking distance, transmitting a third brake braking mode signal to the main control module to decelerate the electric two-wheeled vehicle.