The concept of bitcoin was first proposed by Nakamoto in 2009. It is based on Nakamoto's ideas to design and release open source software and build a p2p network on it. Bitcoin is a p2p digital currency. Point to point transmission means a decentralized payment system. Unlike most currencies, Bitcoin does not rely on a specific currency institution for issuance. It is generated by a large number of calculations based on a specific algorithm. Bitcoin economy uses a distributed database composed of many nodes in the entire p2p network to confirm and record all transactions, and uses cryptographic design to ensure the security of all links of currency circulation. The decentralized nature and algorithm of p2p can ensure that the value of the currency cannot be manipulated artificially by manufacturing a large number of bitcoins. The design based on cryptography can make Bitcoin only be transferred or paid by the real owner. This also ensures the anonymity of currency ownership and circulation transactions. The biggest difference between Bitcoin and other virtual currencies is that its total number is very limited, and it is extremely scarce. The monetary system used to have no more than 10.5 million in four years, and after that, the total number will be permanently limited to 21 million.