Abstract: An effective method for optimal parameter extraction of GP models in bipolar integrated circuits is suggested, Emphasis is placed on processing the iterative equations of GP models, The purpose is to reduce the requirements of the algorithm for initial model parameters and node voltages, And the iterative procedures of solving nonlinear equations for determining intrinsic junction voltages are replaced by an improved method, The method that box constraints are transformed simply is analyzed, A watchdog algorithm is used to find the solution of the constraint problem, Experiments show that the method is very effective for optimal parameters of GP models.