A cooperative replica prefetching mechanism is a new replication strategy aiming to reduce the data access latency in grid by the means of replicating implicit high-value files (IHVFs). The key of this new mechanism is the exploration and location of IHVFs. Locating the IHVFs quickly can improve the performance of the mechanism. This paper employs the DHT (distributed hash table) technology to organize grid nodes to quickly locate the file correlation information which is essential for the query of IHVFs. Considering the specific query pattern, a PTree-based storage structure and corresponding query mechanism for file correlation information are proposed to improve the IHVF query efficiency. Simulation results based on real grid workloads have confirmed the effectiveness and high efficiency of the proposed methods.