Abstract: A new method for the detection of moving dim targets in cloud clutter image sequences is proposed.A detection model of weak targets in cloud clutter background is established based on indiscernibility relation of rough sets(RS) theory, according to the concept that singular local fractal dimension(LFD) will be determined at edges even if the two segments incident to the edge have the same LFD, and the target is detected according to the difference in the temporal of cloud clutter and weak target.Simulation and the experimental results showed that the algorithms are effective in suppressing cloud clutters strongly spatial and temporal related, and they are easy to be implemented.