In order to quickly find out the fault components of the electronic components of the photoelectric radar, and shorten the time of troubleshooting, a fault detection system based on photoelectric radar is designed and realized. System based on VC + + development platform, according to the practical experience of photovoltaic radar electronic components common faults are analyzed. Based on this, a fault tree based on electronic components is established. In the probability of bottom events is given on the basis of the analysis and the probability of top event to occur, to calculate the importance of all parts of the fault tree to the whole system, analysis and comparison of the order of magnitude, to find a larger influence on the system's failure parts.It is verified that the method can quickly find the fault source and the accuracy can be greatly improved by using this method.