Communication protocol detection method, device and system

The invention discloses a communication protocol detection method, device and system, and the method comprises the steps: controlling a first local communication circuit to transmit a detection signal to a first signal conversion circuit, extracting the detection signal through the first signal conversion circuit, modulating the detection signal to generate a first modulation signal, and transmitting the first modulation signal to a bus; the second signal conversion circuit extracts the first modulation signal from the bus and demodulates the first modulation signal to generate a first demodulation signal; the second local communication circuit receives and verifies whether the first demodulation signal accords with a second local communication protocol; if the first demodulation signal accords with the second local communication protocol, the first local communication circuit and the second local communication circuit are in normal communication, otherwise, the first local communication circuit and the secon