Abstract: The flux density distributions on focal plane and other defocused planes of parabolic concentrator were measured with an indirect method based on a CCD camera and a Lambert target. The systematic calibration method was investigated and the characteristics of the spot on every plane were analyzed. The experiment results show that the position of real focus can be obtained by comparing the spot characteristics on each plane; the diameter of the spot is increased, the peak value of flux density is reduced and the shape of the spot becomes more irregular when the amount of defocusing on the receiving plane is increased. The research result can be used for the thermal utilization of the concentrator system and the design of the receiver.