Background radiation noise interference is a difficult technica1 problem for dim signal detection. dim target detection algorithm was proposed which can significant1y improve signal-to-noise ratio (SNR) to achieve uniformly motion dim target detection successfully. Firstly, a coordinate space and a velocity space were established. Then the original image sequence was stacked a10ng different velocity vectors to acquire a new image sequence with SNR improved and the new image sequence forms an image space. Secondly, quasi-target points in the image space were detected by constant false-alarm ratio (CFAR) judging. Finally, velocity vectors and coordinate vectors of quasi-target points were mapped to the velocity space and the coordinate space respectively. As a result, two local peaks from the spaces will confirm true target points. Experiments of real images from actual IR imaging system show that proposed algorithm can improve SNR approximately up to times of original image SNR, and the proposed algorithm is demonstrably superior to compared algorithms on detection probability and false alarm probability.