In this paper time characteristics of dynamic multi-documents summarization has been analyzed by the clustering idea in topic detection technology.From the change of time information threshold value,differ-ent multi-document clustering and multi-documents summarization for the dynamic Web information data stream can be generated.By compared with different threshold values,the importance of time information in a dynamic multi-document summarization is understanded.Experimental result means that you can counterpoise the output of TDT by adjusting α value and generate better quality dynamic multi-document summarization.