Abstract: Based on Hopf bifurcation theory, an improved timedelayed dual model was proposed in Internet congestion control in order to make the stable domain enlarged. The modified model’s dynamic characteristics such as bifurcation condition, bifurcation direction and bifurcation periodic solution are all derived as the communication delay changes. The study shows that the novel model’s nonlinear stability can be described mathematically by three expressions. This paper’s creativity lies in the model’s improvement and its stability’s quantitative description, and it gives the necessary theoretical foundation on designing effective Internet congestion control protocols or algorithms.