Detector array target is a common equipment for measuring the spatiotemporal distribution of laser intensity, and as an important part of detector array target, circuit system's reliability is the key to the efficient and stable operation of detector array target. Firstly, the failure mode and effect analysis (FMEA) of the circuit system is carried out to obtain the influence of different modules on the reliability of the overall system. In order to calculate the reliability of the circuit system, the importance of each module is introduced, and the importance of the traditional AGREE allocation method is improved when analyzing the importance of each module. Subsequently, according to the improved AGREE allocation method, reliability indexes are assigned, and redundancy design is used to improve the reliability of the modules that do not meet the reliability index, so that the reliability of the circuit system operating for 5 h is increased from 0.99931830 to 0.99996730. This study provides a method and basis for the reliability design and distribution of detector array target circuit systems.