In Mobile IP, MN detects its movement according to subnet prefix and router advertisement interval which forms a uniform distribution in the region [min,max]. Therefore, the size of this region has a direct impact on movement detection delay. However, this region is configured statically in Mobile IP, which is inconvenient and inflexible. In this paper, this region is adjusted by using the link bandwidth, and a movement detection delay formula is given. In addition, the proposed method is modeled and analyzed. All the results show that the dynamic region, compared with the fixed region, could reduce the unnecessary movement detection delay drastically.