A method and system for deduplication caching using an unreliable edge resource include acquiring a total storage capacity of all edge servers, searching for candidate cache files by a similarity-based hierarchical clustering (SHC) method, and acquiring file clusters of all the candidate cache files after clustering, where the candidate cache files each include a deduplicated data chunk, and based on the file clusters and an reliability of all of the edge servers, selecting, by a heuristic algorithm, a file cluster from the file clusters to cache to the edge server until a size of cached content reaches the total storage capacity. The present disclosure makes a trade-off between file availability and space efficiency, thereby effectively improving the cache hit rate in the limited edge caching space.