According to the traditional opinion，the tax law belongs to Public Law，which causes all kinds of tax-covered relations guided by the basic legal ideas of Public Law in the tax law.But the Private-Law ideas hidden in the tax legal norms have also played an indispensable role in promoting the formation and development of the tax legal norms. How to construct the new legal ideas of the tax law including the dominant Public-Law legal ideas and the complementary Private-Law legal ideas is significant for the tax law to function in a more effective manner in theory and practice.