Function innovation is the key of product innovation, and function analysis is the precondition and foundation of function innovation. This paper first analyses the importance and necessity of product innovation and function innovation. And then introduces and contrasts two methods of function analysis from TRIZ methodology. On the basis of this, advances a new product innovation method that based on function analysis, and establishes the workflow of this method. Here, Product innovation includes four parts: user innovation, function innovation, principle innovation and structure innovation. Function analysis is the core of Function innovation,Function innovation is the premise of user innovation, and it is also the purpose and foundation of principle and structure innovation. In the end, explains this new method by illustrating a hard drive example.