The invention discloses a method for detecting and calibrating incident postures of light beams in laser interference nano-lithography. The invention is characterized in that in the laser interference nano-lithography, a CCD (charge-coupled device) is used for detecting a light spot formed by each laser beam on the surface of a lithography sample and carrying out computer image processing, the incident posture, including the incident position, the incident angle and the space angle, of each laser beam relative to the surface of the lithography sample is determined through the shape, position and other parameters of the light spot, and the error of each incident posture is further determined through the contrast with the ideal incident posture. A regulating device of the system is used for carrying out corresponding calibration on the incident posture of each light beam. In the method, the CCD is used for detecting the light spots, and a computer is used for processing and determining the incident posture of each beam in a plurality of beams of light, thereby precisely detecting the incident position, incident angle and space angle of each laser beam relative to the surface of the lithography sample and enabling the calibration of incident light to ensure that a final lithography pattern and exposure area to be in line with the design. The method is simple in installation/operation, fast in detection/calibration and conducive to application of the laser interference nano-lithography in industrial production.