Blockchain, originated from Bitcoin, for whose core is decentralized, detrusted, tamper-resistant, unforgeable, and traceable, can be used in management, storage, and circulation of high value data. Blockchain has been applied in a variety of scenarios, but the security problems of blockchain have always existed and have great influence on users' rights and interests. Mimetic defense is a new network defense technology proposed by Chinese research team, which plays an important role in network defense of a new class of system. This paper first introduces the security threats faced by the blockchain and the existing solutions. Then the core ideas of mimetic defense, the typical dynamic heterogeneous redundance (DHR) architecture are introduced. Second, in view of the potential security problems of blockchain, combining the definition of security and parameter selection, dynamic heterogeneous consensus mechanism and DHR signature mechanism are put forward from the ideas of DHR architecture and cryptographic sortition to construct a security solution for blockchain which is called the mimic blockchain in this paper. Finally, the security and property of the mimic blockchain is further analyzed, the result shows that the dynamic heterogeneous blockchain can provide increased security over the typical blockchain in many aspects.