A fast moving-object detection algorithm based on inter-frame Variant Compensated Blocks Difference(VCBD) is presented to deal with the complex scenes with camera scan, dithering and object moving. Firstly, the global motion estimation is performed based on feature points to compensate the inter-frame background. The global feature points in a reference image are selected and matched in a current image. Then, the iteration is applied to realize the minimum sum of position errors of all matched points and to obtain the global motion parameter with the accuracy less than 0.5 pixel. Accordingly, the current frame is compensated to match the background area. Finally, the adaptive variant block difference is proposed to detect moving objects. The whole image is classified into background, foreground and boundary areas and the block is then judged with the threshold and divided into four blocks. These coarse-to-fine steps can greatly improve the velocity and veracity of detection. Experimental results show that the algorithm can detect moving objects in camera scan and dithering sequences and the processing speed achieves 25 frame/s.