Several templates were given based on the structures and variables of a product in creativity templates. As a product has various structures and variables are determined subjectively, the multifarious and nonstandard data add to the difficulties of product innovation. Therefore a new type of product innovation method based on function incentive was put forward. Function common basis was inducted to this model. All product information was represented by the product function model systematically and normatively. Each product sub-function was operated by function dependency, function transformation, function displacement, function relocation and function random excitation strategies. Designer was assisted systematically and directionally to carry out innovative thinking. And the product creative design was realized. Finally, the design process of an agricultural knapsack sprayer was described to demonstrate this model.