The invention discloses a method and system for active replication for a Cache of a multi-core processor. The method comprises the following steps: S1, a host node analyzes the position and access times of a processor core which accesses to a data block in a shared L2 Cache, and selects a candidate replica node; S2, if the accessed times of the data block reach a replica threshold, the data blockis replicated in the replica node and the position of a replica is recorded; S3, if receiving a read request for the replicated data block, the host node forwards the read request to the nearest replica node, and the replica node responds to the data block; S4, after receiving the response, a request node can record the position of the replica node in an address mapping table, and transmits a follow-up read request for the data block to the replica node. The method and the system avoid replica redundancy and unreasonable distribution caused by blind replication, and have the access delay which is close to the low delay of a private L2 Cache, and the capacity which is approximate to the large capacity of the shared L2 Cache.