The paper uses the logistic function as basic modeling function to establish the diffusion superimposition model of innovation products with complementary relationship, and proposes the diffusion superimposition coefficient. The paper also uses this model to analyze the diffusion promotion under imperfect competition. Based on this, the paper studies the evolutionary trend of superposition model with the time’s change, and calculates the balance points of the superimposition model and analyzes. Finally, it analyzes the stability of the balance points of the superimposition model.