Abstract: The study and use of the unknown interval value are still in its infancy．The complex incomplete interval-va-lued information system in which all unknown values are looked as lost was deeply investigated,and then by using grey lattice operation and Hausdorff distance,we provided a new neighborhood relationship in an interval-valued information system．Furthermore,three forms of rough set models were proposed based on neighborhood relationship,maximal consistent blocks and neighborhood system to improve the accuracy of approximations．Moreover,three numerical examples were employed to substantiate the conceptual arguments．

Key words: Rough set,Incomplete information system,Interval data,Neighborhood system,Maximal consistent block,Hausdorff distance