Abstract. In this paper, factors include preferential tax, target enterprise's loss, debt tax shield and depreciation shield are all taken into account. Principal component analysis method is used to construct comprehensive scoring functions and evaluate tax synergistic effects of listed companies after mergers and acquisitions. Parametric and nonparametric tests are employed to analyze the influences of enterprise's asset scale, target enterprise's loss, correlation of M&A, mode of payment and related transaction on tax synergistic effects.