As the quality and importance of Web pages are both variable,paper proposes a static index pruning method which uses the web page importance to determine the ratio of information kept for each document. The result of experiments on GOV2 dataset show that ( 1) the proposed method greatly reduces the storage size and speeds up the search; ( 2) when the pruned index takes only 13% of the original size,P@ 10 and P@ 20 reach or exceed the baseline using full index; and ( 3) by using the proposed method,P@ 10,P@ 20  and MAP are all better than those of the traditional method at the same pruning level.