Compared with the existing speech recognition technology, speech recognition based on a spiking neural network has higher robustness, lower cost, lower power consumption, and more biological basis. Spiking neural network highly depends on spiking signals as input, so an audio coding method for spiking neural networks is necessary. The audio coding circuit in this paper is based on the principle of the human cochlea and is completely constructed by analog signals. It enables audio coding to achieve faster response speed and higher robustness. Based on the principle of human cochlea and the experience of existing audio coding methods, this paper designs a new spike coding circuit for the audio signal. After the audio signal is input into the circuit, the channels of different frequencies have spiking signal output.