The availability of distribution automation is crucial to the entire power system. In this paper, a reliability assessment method for the distribution automation based on IEC 61850 is proposed. First, the fundamentals of IEC61850 protocol and the structure of the distribution automation as well as its main function are illustrated. Then the fault tree analysis method is used to assess the reliability of the system. The probability model is used to calculate the fault rate and repair time, etc. in order to obtain the entire reliability. Next, taken the line fault and bus fault as examples, the fault location and reliability calculation are analyzed. Finally, the proposed method is tested on the RBTS to demonstrate the effectiveness of the method. This work is supported by Science and Technology Project of China Southern Power Grid Company (No. ZBKJXM20170209).