Abstract: Based on the piezo-optic effect of a medium, it is the function of its density, so it's also the function of acoustic pressure. Therefore acoustic pressure in the optical path everyWhere can be determined absolutely by laser- interferometer technique and relative distribution of pressure in the acoustic held obtained from theory or experiment respectively. Principle and method of measurement of pressure in an acoustic field with laser-interferometer as well as theoretical expression of distribution of acoustic pressure in the middle held of one-side radiation of a piston are given in the paper. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique. The results are compared with those measured by the PVDF transducer.