In operating the distribution network system reliability factor needs to be a concern. Therefore, parameters that can be used as references to determine the reliability of distribution of electrical energy is to calculate the index average number of system disturbances during the year is SAIFI ( System Average Interruption Frequency Index ), an index of the average duration of system disturbances during the year is SAIDI ( System Average Interruption Duration Index ), CAIDI ( Customer Average Interruption Duration Index ). Based on the analysis and calculations showed that the value of reliability of the electricity distribution system in the Gejayan substation. GJN 03 feeder and GJN 19 feeder considered less reliable because SAIFI value greater than the standard value of IEEE. All feeder considered reliable because SAIDI value smaller than the standard value of IEEE. For performance rayon, Rayon Kalasan, Rayon Yogya by feeder in the Gejayan substation SAIFI and SAIDI has a value greater than the standart value of WCS and the WCC.