The relationship between R&D polices(R&D subsidy, tax incentives) and firm R&D expenditures is analyzed through firm`s profit maximization function. As a result, the relationship between R&D policies and firm R&D expenditures is determined by the relationship between firm R&D expenditures and market price. In case of major innovation which cause the fall of market price, the elasticity R&D subsidy and firm R&D expenditures is negative(substitution). In case of minor innovation which cause the rise of market price, the elasticity R&D subsidy and firm R&D expenditures is positive(complement). Tax incentives is bring about the increase of firm R&D expenditures. R&D subsidy and tax incentives are substitutively influenced at firm R&D expenditures.