Current solutions solve each component's gas concentration by multiequation inverse calculation, which has disadvantage of introducing parameter errors like noise, constant pool, etc. Based on the photoacoustic spectroscopy detection principle, a novel method for photoacoustic spectroscopy quantitative analysis is proposed using least square regression, and a quantitative analysis model is constructed. Using this method in inverse calculation of the gas concentration can avoid introducing parameter errors. The analysis model is verified by the experiment on the acetylene and methane dissolved in the transformer oil.