Online ballot box system has the advantages of high efficiency and environmental protection, but the existing network voting technology still has a lot of matter. Almost all electronic voting system could be proved to be intrusion. The administrator of the system could tamper with the data for benefit, and the system may be attacked by hackers. The safety and fairness of the existing network voting system depend entirely on the safety and credibility of the website itself, but these cannot guarantee the fairness of voting. Make full use of blockchain technology, so that voting, even if there are malicious participants, but also to ensure the correctness and safety of the vote. The introduction of block chain technology, block chain has decentralized, data tampering and other characteristics. P2P network is applied in the block chain layer to construct a distributed database, digital signature algorithm and encryption technology are used to ensure that the data cannot be tampered with, consensus network algorithm is used to ensure the consistency of the data in the network, and timestamp technology is applied to save the data blocks in a chain structure connected end to end. It paper focuses on the implementation of P2P network networking mode, node block synchronization, data and block verification mechanism and consensus mechanism to ensure data consistency in the network layer of block chain layer. Using time stamp, Merkle tree, asymmetric encryption and other technologies to design data blocks and use chain structure to store data blocks. Combined with the characteristics of blockchain, a fair and transparent voting system is constructed. Model aims to apply the block chain technology to the voting scenario and design a secure block chain voting architecture. It system is designed and developed based on the block chain system. It makes full use of its decentralization, removes the dependence of electronic voting on trusted third parties, and protects the privacy of voters and candidates. Data cannot be tampered with. Once the data are stored in the block chain, it cannot be tampered with. It provides a real and credible database.