A control system for an underwater propulsion apparatus, the control system comprising: a remote controller; and a motor driving device, the remote controller configured for transmitting a wireless signal to the motor driving device, the motor driving device comprising: a communication repeater module; and a motor driving module, wherein the communication repeater module and the motor driving module are wired connected, the remote controller and the communication repeater module are wirelessly connected, the communication repeater module is configured for detecting whether the wireless signal is transmitted by the remote controller, receiving and forwarding the wireless signal, and outputting a corresponding control signal to the motor driving module according to the wireless signal, the motor driving module is communicatively connected to the communication repeater module, and configured for receiving the control signal transmitted from the communication repeater module, and outputting a driving signal for driving a motor according to the control signal, when the communication repeater module fails to receive the wireless signal, the motor is controlled to stop running; wherein the remote controller comprises a magnetic field strength detecting unit, the magnetic field strength detecting unit comprises first and second magnetic sensors (211, 212), a sliding groove, a sliding block, and a magnet, the sliding block is slidably connected to the sliding groove, the magnet is positioned on the sliding block. a remote controller; and a motor driving device, the remote controller configured for transmitting a wireless signal to the motor driving device, the motor driving device comprising: a communication repeater module; and a motor driving module, wherein the communication repeater module and the motor driving module are wired connected, the remote controller and the communication repeater module are wirelessly connected, the communication repeater module is configured for detecting whether the wireless signal is transmitted by the remote controller, receiving and forwarding the wireless signal, and outputting a corresponding control signal to the motor driving module according to the wireless signal, the motor driving module is communicatively connected to the communication repeater module, and configured for receiving the control signal transmitted from the communication repeater module, and outputting a driving signal for driving a motor according to the control signal, when the communication repeater module fails to receive the wireless signal, the motor is controlled to stop running; a communication repeater module; and a motor driving module, wherein the communication repeater module and the motor driving module are wired connected, the remote controller and the communication repeater module are wirelessly connected, the communication repeater module is configured for detecting whether the wireless signal is transmitted by the remote controller, receiving and forwarding the wireless signal, and outputting a corresponding control signal to the motor driving module according to the wireless signal, the motor driving module is communicatively connected to the communication repeater module, and configured for receiving the control signal transmitted from the communication repeater module, and outputting a driving signal for driving a motor according to the control signal, when the communication repeater module fails to receive the wireless signal, the motor is controlled to stop running; wherein the remote controller comprises a magnetic field strength detecting unit, the magnetic field strength detecting unit comprises first and second magnetic sensors (211, 212), a sliding groove, a sliding block, and a magnet, the sliding block is slidably connected to the sliding groove, the magnet is positioned on the sliding block.