Montesquieu’s separation of powers doctrine is a part of the political power theory，but the theory of separation of powers doctrine does not reveal obstacles in the process of implementation of decentralization. To understand the key point of decentralization theory,we should clarify the relationship between power and truth. In any country, the advanced social class or the political party who declare they have grasped the truth always try to evade the discussion of the separation of powers doctrine when they gain power and exercise the power vigorously. This shows that the view of truth is contradictory in nature with the separation of powers doctrine. Because of this, the class claiming possession of truth use the view of truth to defend their monopoly of state power in initial distribution of power.