If we assume that the database is a book, the reading and writing database can be regarded as a kind of bookkeeping behavior. The principle of block chain technology is to find out the fastest and best person who has the fastest account in a period of time. The person is the person to keep the account, and then send the page information to all the others in the whole system. This is equivalent to changing all records of the database to all other nodes in the whole network, so block chain technology is also known as distributed account.