The dependences of light intensity,open-circuit voltage,short circuit current and cell′s temperature on the distance between the Fresnel lens and solar cell are investigated in concentrating photovoltaic system.The results show that the efficiency increase of concentrating photovoltaic system mainly results from the improvement of the short-circuit current,but not from the open-circuit voltage.It is found that the output power of solar cell can achieve maximum when the cell is placed at the focal point of the Fresnel lens.But the maximum efficiency of a concentrating photovoltaic cell per unit of light intensity can be obtained only when the cell is placed before the lens focus.It is of great guiding significance for the design and research of the current photovoltaic systems.