Fourquadrant pulse converters were widely applied in electric traction drive systems. IGBT was the core device of the fourquadrant pulse converter, which was prone to fail. IGBT opencircuit fault detection for fourquadrant pulse converters was studied. Firstly, the characteristics of the opencircuit faults were analyzed. Then the average value of the grid current was divided by the average value of the current’s absolute value as the detection variable. The detection variable under different power level and each fault was analyzed and the threshold was decided by the detection variable with rated power. Finally, the effectiveness of the detection method was verified by hardwareintheloop simulation.