A hybrid algorithm for determining the slant - range visibility using lidar data in the low - visibility atmosphere is proposed,considering mu ltiple - scattering effects.In the algorithm,the mathematical relation of the slant - range visibility and the atmospheric optical depth is firstly deduced according to Koschmieder law.Secondly, the optical depth is derived from the multiple - scattering lidar equ ation,taking advantages of multi - elevation angles. Meanwhile,the ratio of scattering coefficient for multiple scattering to that f or single scattering is calculated by semi - analytic Monte Carlo method.In the end,the slant - range visibility is obtained,wi th the consideration of multiple - scattering effects.The proposed algorithm has been used for retrieving the slan t - range visibility from returns of a ground - based lidar operating in vertical detection status.The results show that the re lative error of the obtained slant - range visibility with and without considering the multiple - scattering effects is up to 9%.It is noted that the multiple - scattering effects may become more significant as the visibility decreases.This is demonstrated by the increase of the ratio of scattering coefficient for multiple scattering to that for single scatt ering.Therefore, in order to accurately retrieve the slant - range visibility using lidar data,the multiple - scattering effects have to be considered,especially for the condit ion of low -visibility atmosphere.