Background: Bitcoin system, when more than 51% computing power is controlled by a single node, the block chain can be distorted maliciously. This is called 51% attack which is a well-known potential risk that could destroy the Bitcoin system.MethodThe paper proves that under the current proof-of-work mechanism, computing power eventually will be centralized at a single node if miners are rational enough.ResultThe paper propose a new proof-of-work mechanism that improves decentralization and reduces the risk of 51% attack without increasing the risk of Sybil attack.ConcusionsThis new mechanism introduces a series of principles such as Career open to all talents, without distinction of birth, Distribution according to labor and All Men are created equal.