The content ratios of four elements in Cu(In, Ga)Se2 (CIGS) thin film have great impact on performance of the thin film. CIGS thin films are deposited by magnetron sputtering at different work pressures, and the laser induced breakdown spectroscopy is used to quantitatively analyze the ratio of Ga content to In and Ga contents, as well as the ratio of Cu content and In and Ga contents. The spectral intensities of elements in CIGS deposited at different working pressures are analyzed, the results show that the intensity ratio of Ga spectral line to In and Ga spectral lines is corresponding to optical band gap, and they increase initially and then reduce with the increase of the work pressure, and the maximum optical band gaps are achieved at the pressure of 2.0 Pa, the intensity ratio of Cu spectral line to In and Ga spectral lines is nearly invariable corresponding to the value obtained from energy spectroscopy. The rapid detection of element content proportion in thin film can be realized by LIBS technology, the relative ratios of different intensities of spectral lines can indirectly reflect the element content ratios in thin film, which indicates the potential of LIBS technology in thin film analysis, providing method and technical support for optimizing working parameters in CIGS preparation by magnetron sputtering.