Laser-induced breakdown spectroscopy, as an optical technique for material component analysis, was successfully developed and applied for the detection of atmospheric water vapor. By detecting moist air with different humidities, the spectral intensity of H is found to be a linear enhancement with the increase of relative humidity. A model for the comprehensive analysis of H and O atomic spectral lines is established, and a good correlation coefficient is obtained. Moreover, air samples containing elemental impurities are also detected, and the clustering analysis is realized using principal component analysis. Based on the internal standard method, the quantitative analysis of Na and Mg elements is realized by choosing a spectral line of N as the internal standard line.