Abstract: Taking project of managing distribution network of Jining, the paper introduced structure, main parameters, functions and actual application of FDR4011-GSM fault detection device of distribution automation, and analyzed principle that the device processes two interphase short circuit faults of radial line and ring network line in details. The analysis result showed that the device can realize rapid and automatic diagnosis and isolation of interphase short circuit fault and has good operability, real-time performance and reliability.