The legalization of interest relationship is an important aspect of the legal construction of private schools, which not only carry public interest, but also pursue private interest. This involves a variety of specific interest relationship, including the relationship with national interest, social public interest and private interest. Interest is closely connected with law, particularly with the financial and tax law. By confirming the attribution of interest, harmonizing conflicts of interest and promoting the realization of interest, the financial and tax law realizes the legalization of the interest of private schools. While China's current financial and tax law of private schools embodies the cognitive logic of the legalization of finance and taxation, there remain some limitations, which should be overcome through providing equal nonprofit support to both private and public schools, offering preferential taxation policy to the founder of nonprofit schools, and affording a handsoff policy to the establishment of forprofit compulsory schools and so on.