Small target detection is a critical problem in the Infrared Search And Track (IRST) system.Although it has been studied for years, there are some difficulties remained due to the clutter environment such as the cloud edge and the horizontal line.In the homogeneous area such as sky, cloud-inner area and sea surface area, target can easily be detected, but in heterogeneous area which contains cloud edge, sky-sea line the target may be falsely detected.This paper proposes a novel method called accumulated center-surround difference measure to detect infrared small target in heavy clutter.Each pixels accumulated center-surround difference measure is computed by using sliding window manner.The measure can effectively distinguish target region and heterogeneous region.Experimental results show our method achieves better performance.