To solve the problem of adverse selection and moral hazard, accounting is characterized decision usefulness and the validity of contract. Because the information useful in decision-making cannot ensure the validity of contract ,there is a inconsistency between decision usefulness and validity of contract. As a result, formulating accounting standard in reality is harmonization between the two ones, and goodwill accounting policy selection is in true a delicate balance between decision usefulness and validity of contract. Endeavor to optimize goodwill accounting policy selection don't only lie in its aspect of technique but lie in analyzing and researching accounting environment such as economic one, social one,institution one and so on , and the information demand and inconsistency of various social group of accounting interest, and lie in continually improving the mechanism of accounting-standard-making.