Abstract:A united computational model of hydraulic，mechanical and electrical parts in the hydropower system was built，and the two-order predictor-corrector method was used to assure both of the computational precision and speed. The object-oriented programming language VC++ was used to write the program of the each part，and enclosed into an icon，sequentially，the universal icon library for the hydropower system was established. The effect of operation characteristic of the unit was analyzed under the fluctuation of the power network，it is shown that the power angle，d-axial voltage and q-axial voltage of the generator are clearly affected by the fluctuation of the power network voltage，and the power，the rotating speed of the generator and the water level in surge chamber are observably influenced by the fluctuation of the power network frequency，the fluctuation of the power network phrase angle can lead to the fluctuation of the operation parameters，but it can come back the previous balance condition. While the power network fluctuates

the hydraulic and electrical operation parameters will affect each other by the adjustment of the governor and the excitation system，and the fluctuation frequency of the electrical parameters of the generator is equal to the natural frequency of the water hammer.