For the purpose of detecting and locating faults in time during the running of adaptive optical wave-front processor based on Field Programmable Gate Arrays (FPGAs), a fault diagnostic system (FDS) is proposed for this wave-front processor.According to the requirements of debugging and operating, the system can provide real-time feedback of the results and states from each part of the wave-front processor to upper PC, locate faults, and analyze data error.The fault diagnostic system was tested on 137-unit adaptive optical wave-front processor platform.Experimental results indicate that the feedback data from the monitor system and the relevant information are pretty matched with the corresponding theoretical values, and FDS can also detect and locate the faults in time, during the real-time correction of the processor.The system is applied in the large foundation of high resolution imaging telescope adaptive optical system, which is able to reflect the process and relevant results of the adaptive optical wave-front processor intuitively, detect and locate the source of faults in time if faults occur, and greatly improve the testing efficiency in both hardware and software.Meanwhile, analyzing the results from each stage contributes to improve the calculation speed and precision.