The open circuit voltage changes with the distance between the lens and the solar cells in the concentrating photovoltaic system is studied through the experiment. The voltage peak appears during the distance change. It is confirmed by theoretical analysis that the peak appears due to the open circuit voltage changes with the distance into a Gaussian distribution,and maximum output voltage appears when the light focuss depletion area through fitting the experimental results. In addition,it is studied through the experimental study combined with theoretical analysis that there is logarithmic relationship between the maximum output open-circuit voltage and illumination. It is of great guidance for the current photovoltaic system design and research.