Abstract: The application of solar radiation models is,to some extent,limited by the randomness of weather variations and complicated and various influencing factors. This paper discussed the feasibility of using the atmospheric transparency coefficient as a basis for weather classification,extended the definition of the coefficient of atmospheric transparency to complex weather conditions and corrected the influence on the solar altitude angle. Further,a weather classification method based on the atmospheric transparency coefficient was proposed,and its application in the direct solar radiation models was listed to illustrate the effectiveness of this method.