Linear regression theory is introduced to analyze the process of photoacoustic image and the algorithm of multi-wavelength component concentration distribution is constructed. Computer simulation and biological tissue sample experiment are carried out to prove that the algorithm can make photoacoustic image reflect more biological tissue information. During the experiment, all parameters are kept as constant except the wavelength of exciting pulsed laser. The result shows that the information reflected by photoacoustic image of single wavelength matches well with the absorption of mixture component at excited wavelength. Photoacoustic image of single length cannot fully indicate the distributions of each component when the component absorptions are quite different. Based on this, the distribution information of image components changes and matches well with real sample after being treated by the algorithm.