The invention discloses a forest canopy measurement method. The method can observe and measure a forest canopy and a single plant canopy. An instrument for realizing the method comprises cameras and accessories, including three cameras, a filter and a tight shot, wherein, one camera is a near infrared camera; and the instrument also comprises a mechanical control partconsisting of a tripod head which can adjust the direction of an azimuth angle and a zenith angle, a measurement tripod fixed below the tripod head, and a simultaneous exposure device consisting of two receivers of remote-control system of the camera, a remote controller and a mechanical shutter line; and the three cameras are arranged on a long arm which is driven by the driving mechanism of theazimuth angle and the zenith angle of the tripod head. The invention can solve the problem that the traditional parameter measuring method has the disadvantages of poor precision and low efficiency, can obtain the single plant canopy image for calculating the geometrical parameter, and can obtain canopy near infrared image for measuring gathering index and non-photosynthetic ingredient amending parameters.