On the basis of the function of self/nonself recognition of natural immune system,a new immune recognition algorithm based on negative selection is presented.In proposed algorithm,the generation of detector set is improved and a new matching rule is also introduced to online matching detection.Moreover,the prior knowledge of the known target samples and the content update of the detector set are also considered.The proposed immune recognition algorithm is applied to detect and recognize the air targets,not only are the known types of targets detected and recognized,but also the unknown types of targets are detected.Experiment results show that the undetected error rate,the misrecognition error rate and the detection precision are 0.375%,0.006% and 99.563%,respectively.Meanwhile the detection process demonstrates good robustness for different targets.