In this paper, based on the principle of slant visibility detection, the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model is used to solve the radiation transfer equation, and detailed theoretical simulation and analysis of the sky background radiation are carried out. First, using the aerosol models from SBDART model, the sky background radiation results of different types of aerosol models under sunny conditions are obtained. The distribution trends of solar direct radiation and atmospheric scattering radiation at different heights are discussed. The influences of single scattering radiation albedo and asymmetry factor on the results are analyzed. A calculation method combined with Lidar and SBDART model is presented to obtain the real sky background radiation. The aerosol data obtained by a scanning lidar is taken as the input parameter of SBDART model, and the distribution results of solar direct radiation in the real atmosphere and sky background radiation at different heights are calculated. In order to validate the correctness of the results, the solar direct radiation synchronously measured by the solar photometer is compared and verified. The results show that a consistent change trend can be obtained between them, showing positive correlation with a correlation coefficient of 0.99. Finally, taking blackbody as the target, the influence of sky background radiation on slant visibility is preliminarily discussed. The actual sky background radiation obtained by combining Lidar and SBDART models can provide guarantee for accurate inversion of slant visibility.