According to the requirements of “detailed specification of practicality acceptance for distribution automation systems”, four assessment indicators, including terminal online rate, correctness rate of remote signal, remote control usage rate and remote control success rate, are focused. At present, the researches about the operation and maintenance index of distribution automation mainly focus on the calculation methods, and are lack of the researches about the factors of influencing test index and its influencing degree. A practical analysis method of distribution automation based on fault tree is proposed. Combined with the indicator characteristics of the distribution automation operation and maintenance, it analyzes influencing factors of each index and establishes fault tree model. According to the proportional sharing principle, the contribution ratio of each factor of each operation and maintenance index is calculated. The weak link of each operation and maintenance index is identified. Then according to actual operation and maintenance condition, the technical advice and management measures are proposed to optimize the evaluation index of the distribution automation. In the actual operation and maintenance, the factors with higher allocation rate is monitored and rectified to improve the operation and maintenance index of distribution automation and ensure the normal operation of distribution automation.