The invention discloses an optical method, a device and an application for measuring supersonic wave sound pressure and sound intensity The optical method comprises steps illuminating the supersonic wave by a parallel beam in a direction perpendicular to the propagation of the supersonic wave, obtaining a diffraction frequency spectrum of a raster, receiving zero order spectrum diffracted light, obtaining a corresponding voltage value through a reversing and amplification circuit and a sampling processing circuit, obtaining the amplitude of the sound pressure to be measured by comparing with a calibration value obtained beforehand and calculating the sound intensity. The device provided by the invention comprises a power supply, a signal compensation circuit, a signal collection circuit, the signal reversing circuit, the signal amplification circuit, a computer, a light source, a light outgoing diaphragm, a light outgoing window, a light incident window, a convex lens, a filtering diaphragm and a photoelectric detector, wherein the light source, the light outgoing diaphragm, the light outgoing window, the light incident window, the convex lens, the filtering diaphragm and the photoelectric detector are successively arranged along the heading direction; the light source is connected to the power supply and the signal compensation circuit; the photoelectric detector, the signal reversing and amplification circuit, the signal compensation circuit, the signal collection circuit and the computer are successively connected. The invention has strong measurement directivity and practicability.