Abstract: In mobile computing environments,how to keep cache consistent in mobile client is a hot research spot. Broadcasting of invalidation reports is an efficient method,but it’s difficult to choose the time window of invalidation reports because parameters are varying with environments and time. The time window of invalidation reports must be adjusted continuously while parameters are being updated, to ensure that the network system is working efficiently. In this paper,the formula for computing the time window of invalidation reports in theory are proposed,the reasonable value is analyzed,and the algorithmic implementation is provided.