The association detection of dim small moving object in infrared image sequences was studied.Based on multi-hypothesis “K/N” regulation was adopted and credibility was introduced as noise probability distribution function.Multi-hypothesis and “K/N” regulation were organically combined which could overcome such problems of the former as large computation cost and inability for real-time processing.Credibility is helpful for improving the robustness of detection and the method has high detection probability even when there is noise pulse and cloud coverage.Theoretical analysis and real data test prove the feasibility and effectiveness of the method.