Abstract: Analyzes quantitatively the relationship between Nash balance points of multi-user non-linear network systems and the price difference between different priorities of these systems. Develops a mathematical model in terms of user's surplus function and relates it with the surplus function of the network systems. Difference method is used to illustrate the effect of each and every price difference between priorities of the systems when reaching Nash balance point, and a quantitative method is given to determine the position of a balance point from the range of values to take for each and every price difference between priorities, thus giving the condition on which the network systems will come up to Nash balance with Pareto optimality. A numerical example is given to show how to analyze a two-user and two-priority network system. Discusses the effect of price difference between priorities on the service selection for users and the balance of systems. The effectiveness of the method proposed is thus verified.