A new method is proposed to detect infrared small and dim targets in cloud cluster image based on fuzzy classification.Firstly,according to the infrared imaging principles,dim and small targets in cloud cluster image can be divided into three classes,which are the edge class,the inner cloud and clear sky class,the target class.By analyzing different classes,the classified models for each class are established.And then four-direction pixel feature vector is defined to describe different classes.Finally,based on the fuzzy classification theory,class correlation coefficient is defined to classify each pixel of the infrared image.Experimental results show that the proposed method can separate dim and small targets from the cluster in low signal-to-clutter ratio (SCR) infrared cloud images efficiently.