An in-vehicle protection system includes a signal input interface and a vehicle protection circuit. The signal input interface is arranged to receive at least an indication signal indicative of a status of a vehicle. The vehicle protection circuit includes a first processing unit, a second processing unit, and a controller. Each of the first processing unit and the second processing unit is capable of performing vehicle protection upon the vehicle, where computing power of the first processing unit is different from computing power of the second processing unit. The controller is used for receiving the indication signal, outputting the received indication signal to the first processing unit for further processing when the in-vehicle protection system operates under a first operational state, and outputting the received indication signal to the second processing unit for further processing when the in-vehicle protection system operates under a second operational state.