Abstract: Hydraulic turbine models are the most complicated in the simulation of hydraulic transient process. They are typically solved with an iterative method, but numerical divergence frequently occurs in the calculation. To overcome this problem, this paper describes a new single-point iterative procedure that is optimized to improve the convergence of hydraulic turbine models. A maximum step size has been analytically derived for numerical iteration, and the influence of various parameters of the hydraulic turbine on convergence analyzed. Results show that this new method can greatly reduce the numerical divergence and would provide a reliable theoretical basis for modeling hydraulic turbines.