Abstract: Shape feature is one of the important characteristics which are used to describe images in MPEG7. The descriptor of Cluster of Concentric Discrete Circles (CCDC) can be extracted in a short time. However, the method uses the variance of the ring arc segment as characteristic in its feature function; it is because that the discrete points of inner and outer circle are different. The feature values range of inner and outer circle are also different, and then it leads to produce characteristic covered up phenomenon. For the above problems, the feature functions are redesigned in this paper. The relative arc length of the arc segment or segments is used as a feature. Each ring characterized is expressed by four sub-features, and each feature value is normalized to the range of 0~1, the extraction process is more simple and faster than that of the original CCDC descriptor. The new method is called Improved CCDC (ICCDC). In this paper, all experiments are done by using the MPEG7-CE1-B standard shape database, and the performance is evaluated by the Precision-Recall curve. The experiments show that the performance of the improved CCDC is better than that of the original method. And the retrieval precision is 50% higher than that of the original method, and the time of extracting all the shape in MPEG7-CE1-B is reduced about 25 ms than that of original method.