The primary data sampling methods of Fourier transform infrared (FTIR) spectrometer include He-Ne laser triggering method and Brault method. The Brault method uses the hardware counter and the collected data has time delay, which may lead to the increase of subsequent data processing time. Therefore an improved data sampling and processes method based on the Brault method is proposed. The method adopts the synchronous data acquisition card, and samples two-path data simultaneously, to get the precise zero crossing information of He- Ne laser with approximate similar triangle method. Interference signal is resampled according to the cubic spline interpolation method, and the software data sampling and processing is realized. In addition, the spectra obtained by the He-Ne laser triggering method and the proposed method are compared. The comparison results show that the background of H2O and CO2 absorption peaks in spectra obtained by the two methods are consistent with the standard absorption spectra, the improved data sampling and processing method based on the Brault method improves the signal-to-noise ratio of the spectrum, and the laser zero crossing information can get the stability of the moving mirror scanning speed. However, sampling and processing time for the He-Ne laser triggering method is less than that for the improved Brault method.