Based on the dark channel prior, we propose a dehazing algorithm for single image, discuss the adjustable parameters of the algorithm, and analyze the impact of parameter variation on the final dehazing results. In the primal algorithm, the sky area is mentioned as no need of special handling. However, we find that this area needs to be treated separately. We set threshold to isolate the sky area separately and receive better effect. Meanwhile, we study on the introduced guided-filter, and analyze the impact of parameters on the real-time performance of the algorithm. In order to improve the real-time performance of the algorithm, we reduce the picture firstly in order to shorten the calculation time, and then enlarge the image by image interpolation method to get haze-free image. The experimental results show that the operation time of the algorithm can be reduced by 85.7% with the premise of image haze removal.