A real-time adaptive non-parametric thresholding algorithm for change detection is proposed in this paper. Based on the estimation of the scatter of regions of change in a difference image, a threshold of each image block is computed discriminatively, then the global threshold is obtained by averaging all the thresholds for image blocks. The block threshold is calculated differently for regions of change and background. Experimental results show the proposed thresholding algorithm performs well for change detection with high efficiency.