In order to reduce interference of modulation noise, a three stages Savitzky-Golay denoising method was proposed applied to the gas concentration inversion based on direct absorption spectroscopy laser detection. Taking near 6 612.939 cm-1 absorption line of NH3 molecular as a test object, the experiment results show that the root mean square error of NH3 original absorption spectrum signal was decreased from 8.53 to 1.01 by three stages Savitzky-Golay denoising method, the SNR of NH3 absorbance profile was increased by 3.3 times; 5% standard NH3 was measured five times in succession, which the average deviation of inversion value was 0.0743%, and the relative standard deviation was 1.4%. The inversion value was better than that of db6 wavelet denoising and non-denoising. The accuracy of gas concentration inversion can be improved when the original absorption spectrum signal was processed by three stages Savitzky-Golay denoising, which can provide reference for the on-line laser detection of high-concentration industrial gas.