First of all，in this dissertation，development of western tax principles and the transition of tax principles from the founding of China to the Third Plenary Session of the 18th CPC Central Committee was studied based on the tax principle. Next，the necessity and feasibility of applying tax principles in the design of PPP tax optimization path by the theory of tax principles was analyzed according to the characteristics and complexity of each stage of the whole life cycle of PPP project. In addition，a lot of problems，including the “inconvenience” of tax revenue due to the lack of special tax policy provisions，the blank of tax collection and management，repeated taxation，and the failure of tax policy to play a regulatory role in response to the unique risks of PPP projects，was pointed out according to the principle of “unified tax system，fair tax burden and promotion of fair competition”. Finally，four optimization suggestions have been put forward for tax policies of PPP projects，including elimination of tax “inconvenience”，realization of tax certainty，avoidance of double taxation，prudent preference and optimization of resource allocation by applying tax principles.