The progressivity of personal income tax system reflects the extent of its equitable distributionAccording to the literature of home and abroad, the affection of progressivity of personal income tax system can be divided into five factors including tax rate structure, allowance, deductions, tax incentives and tax evasion On the basis of the relative concentration curve of Kakwani and the individual income tax system model of Pfhler, we build the decomposition model of progressive personal income tax system and propose the basic design ideas of progressive personal income tax system based on the model conclusion