As the front processing unit in an infrared imaging system,target detection is one of the important parts in precision-guidance and is also a critical technique or difficult problem.Only if the target in the scene is detected in time,a series of subsequent processing such as target tracking,target recognition and so on can be implemented smoothly.To find the target as soon as possible so as to let the system have enough time to react against it,the target must be detected at a very long distance. Therefore,the detection of the target in a complicated infrared scene becomes a very urgent problem to be solved.The discovery and study of new theory and algorithms for small target detection and how to use the current detection theory in small target detection is still a most important subject and is of great significance.