Performance of the photovoltaic system is highly influenced by the weather, especially the irradiation and the temperature. To simplify the design of solar generator power, a mathematical model and its validity of the solar cell are required. In this work, the value of the parameters in the mathematical model is obtained by the measurement of the I-V curve of the module. To get an I-V curve, one of the modules in the system was radiated and loaded by a load simulator. A photovoltaic pumping system with maximum power point tracker was built and tested. The results were analyzed and evaluated by using the parameters and the photovoltaic system was shown to be well optimized. (C) 2002 Elsevier Science B.V. All rights reserved.