The concept of bitcoin was first proposed by Nakamoto on november1,2008, and was officially born on january3,2009. The open source software designed and released according to the idea of Nakamoto and the P2P network built on it are a kind of digital cryptocurrency for peer-to-peer (P2P) transmission, with a total of 21million pieces. Bitcoin is generated through a large number of calculations based on a specific algorithm and duses not rely on a specific currency institution to issue. It uses a distributed database composed of many nodes in the entire P2P network to confirm and record all transaction behaviors, and uses cryptography design to ensure the security of each link of currency circulation, which can ensure that the currency value can not be artificially manipulated through a large number of bitcoin manufacturing. The design based on cryptography can make bitcoin only be transferred, paid and cashed by the real owner, and also ensure the anonymity of currency ownership and circulation transactions.