In order to recover the degraded image induced by the fog or haze, this paper proposes a single image dehazing algorithm based on adaptive dark channel prior. The error during the estimation of transmittance by Dark Channel Prior(DCP) will directly cause Halo effect. To deal with this problem, the notion of Adaptive Dark Channel Prior(ADCP) was proposed, it means using adaptive in the acquisition of DCP, it can reduce the effect brought by the change of depth of focus, So it will obtain the transmittance correctly without the use of Guided Filtering(GF), this means it will avoid low efficiency and defog incomplete caused by the filtering. Experiments show that the improved dehazing algorithm could eliminate the Halo effect and achieve the dehazing image with high contrast, high color saturation and abundant details from both objective or subjective imagequality assessment. Meanwhile, the speed of image process is also improved.