In a method for compressing data, a storage system determines whether deduplication can be performed on a target data block. When deduplication cannot be performed on the target data block, the storage system obtaining a similar fingerprint of the target data block, and determines, based on the similar fingerprint, a combined data block group to which the target data block belongs. The storage system then performs similar compression on the target data block based on a reference block in the combined data block group.