The invention discloses a method for calculating multilayer medium sound velocity based on photoacoustic imaging technology. The method comprises the following steps of: carrying out inverse filtering processing on original data received by a sensor so as to obtain inverse filtering data according to a pulse response function of the sensor; setting initial sound velocity and sound velocity iteration range of different media in a tissue; carrying out photoacoustic image reconstruction based on the inverse filtering data and the set sound velocity of each layer in the tissue; calculating from photoacoustic images reconstructed each time and extracting the distribution of sound sources in the image, and determining whether the iteration is finished according to the distribution information of the sound sources, and outputting the sound velocity if the iteration is finished. A simple and noninvasive method for measuring the sound velocity in a biological tissue provided by the invention is simple to calculate, low in complexity and outstanding in effect.