Abstract: Regulation and cleaning up tax incentives is the only way to realize the rule of law and realize fair competition. For a long time, under the trend of thought of the legal doctrine, the alienation of the tax preference has destroyed the environment of fair competition. Specific to the Shanghai Free Trade Zone tax incentives, in the affirmative on its innovative, scientific basis, in the next area of tax incentives have a lot of room for improvement. First of all need to implement the tax legal principle, premise in the rationality of the card, do the legitimacy of FTA preferential tax certificate; secondly on the value orientation of the legislation, tax neutral oriented, to prevent the destruction of competition policy. Finally in the legislation of the ex ante and ex ex post evaluation price, should be included in the principle of proportionality as a basis for consideration of tax preference legitimacy.