This paper mainly aims at the modeling problem of the PV (photovoltaic) array under the background of a 30Kw PV grid-connected generation system. The iterative method of the time-varying parameters is proposed to model the plant of the PV array. Then, the results about the relationship of PV cell and PV array and the uniqueness of the solution are obtained respectively. Finally, the PV grid-connected generation system is given to demonstrate the effectiveness of the proposed method, by comparing the model output with the actual output of the system.