A controlling system for an electric bicycle is connected to a CAN bus of the electric bicycle and a controlling end, and configured to control a plurality of electric elements which are signally connected to the CAN bus. A dongle module includes a first connecting port, a dongle and a second connecting port. The controlling end is configured to transmit a USB signal to the first connecting port. One end of the dongle is coupled to the first connecting port, and the dongle is configured to convert the USB signal into a CAN signal. The second connecting port is coupled to another end of the dongle. A console includes a console port. The console port is detachably connected to the second connecting port and coupled to the CAN bus. The CAN signal is transmitted to the CAN bus via the second connecting port and the console port.