Dim target detection in infrared image with complex background is always a complex and difficult task in remote sensing area. A spatial Signal-to-Noise Ratio(SNR) dim target detection scheme with multi-frame accumulation for high frame rate imaging system is designed. At the same time, according to the continuity of the target motion, the multi-frame confirmation method outputs the real target trajectory. The experiment shows that the average operation time of the algorithm on vs2013 is 23 ms, and it can effectively detect infrared dim target with SNR of 2.91. Otherwise the method has an adaption to multi-target detection.