Abstract: In order to measure the flux density distribution of parabolic trough concentrator,an indirect method and a test system are studied and proposed. The test system based on the method is composed of a standard Lambert reflector,a CCD imaging system,a linear guide and an adjusting mount. The Lambert reflector and the CCD imaging system are strictly calibrated by a designed radiometric calibration system. Then the relations between flux density and the response of the CCD system are obtained. Experiment of flux density distribution of parabolic trough concentrator is performed by this system. Through the introduction of this system,the calibration method,every component part and key designing technologies are all introduced in detail. The results indicated that the error of flux density system is less than 5% through field test and experiments.