Abstract: This paper proposed a MDL(Minimum Description Length) principle based dynamic community partition algorithm that is named DCI (Dynamic Community Identification).This paper defines evolving relationships between static communities at adjacent time points,so that DCI can not only identify the dynamic communities with different life cycles but also describe their evolving processes accurately.Experiments demonstrate that the DCI algorithm can identify dynamic communities more accurately than the existing algorithms and it's applicable to processing large scale dynamic networks in acceptable time.