The synthetic aperture radar (SAR) closed-loop test system is constructed to simula te ground-satellite signal transmission process for obtaining SAR system imaging f unction, compression mode and point target characteristics. Those are of great significa nce during HJ 1 C SAR system test. Firstly, the paper presents the SAR echo signal gener ation and the physical implementation of echo simulator, and then provides metho ds to build SAR closed-loo p test systems using echo simulator under wired and wireless manner. Finally, the paper gi ves the point target performance results of HJ-1-C SAR system based on the closed -loop test system. Test results show that the closed-loop test system meets the testing needs of HJ-1-C SAR system and has good engineering application value.