The detection ratio of dim target with low signal-noise-ratio (SNR) in cloud background especially using low frame frequency detector decreased notably. Optical flow histogram (OPH), its characters is proposed, and its character is presented. Then the reason of low target detection radio from infrared image using low frame frequency detector is analyzed. And based on this analysis, an algorithm of infrared dim target detection based on background motion compensation is advanced. This algorithm uses OPH to compute the background motion vector, and make background compensation. By distinguishing movement difference between target and background, the comparison result is gained. In order to reduce the false alarm, this result is filtered by Robinson filter to reduce the residues edges. The experimental results have proved that this algorithm can improvegreatly the probability of infrared point target detection, and detect dim targets with SNR of 1.