The invention discloses a method of implementing simultaneous transmission of digital signals and audio signals in a fire-fighting telephone system. The method of implementing simultaneous transmission of digital signals and audio signals in a fire-fighting telephone system includes modulating an audio analog signal to a direct current power supply to form an audio analog signal of a direct current component; superposing a digital signal that the bandwidth is higher than the audio analog signal on the audio analog signal of the direct current component to form a mixed signal; modulating the low level pulse of the digital signal to a bus in a voltage mode, and performing digital coding through the width between two low adjacent level pulses on the bus; modulating the audio analog signal to the high level of the bus, issuing the audio analog signal to an extension set; receiving the audio analog signal by the extension set and performing digital signal and audio analog signal demodulation; converting the digital signal issued under the voltage mode modulation into a current being higher than the bandwidth of the audio analog signal by the extension set, and loading the current to the bus to form a current loop and returning the current loop in an interval bit mode. The method of implementing simultaneous transmission of digital signals and audio signals in a fire-fighting telephone system has the advantages of simultaneous transmission of audio analog signals and digital signals, noninterference, long transmission distance, low distortion rate, and high driving capability.