The traditional single image dehazing algorithm based on dark channel p rior (DCP) is accompanied with shortages such as the white border in the scene and the high computational complexity.In order to solve these problems,this paper proposes an improved algorithm based on t he median dark channel prior (MDCP). Firstly,the absolute value of the minimum of RGB three color channels and t he median dark channel are used to determine whether dark channel prior or median dark channel prior is applicable.If dark channel prior is applicable,the dark channel prior value of bigger window is dec ided as the final value of dark colors.Otherwise,the smaller median dark channel prior value of two wind ows is used to present the final value of dark colors.If neigher dark channe prior nor median dark channel prior is not applicable,the median dark channel prior value of smaller window is chosen as the final value of dark colors.Then it retains the hue in HSI color space,the intensity is d efogged using the modified dark channel values,and the saturation is improved to adopt color rest oration.This method does not need the image post repairing.Experimental results show that the improved algori thm is effective and feasible.