Due to the error of digital sampling, there is a deviation between the zero optical path difference (ZOPD) detection position of the interference signal in the infrared gas analyzer and the actual position. To solve this problem, a high-precision detection method of the ZOPD position based on wavelet transform is proposed. Firstly, the wavelet envelope curve of the interference signal is obtained by the wavelet transform, which can obtain the phase information and amplitude information of the maximum modulation position, and then the optimal ZOPD position is calculated by using the amplitude and phase information. The experimental results show that the error of the wavelet transform method is 19.617 nm, and the relative error is reduced by 93.11% compared with the peak method.