The invention belongs to aviation detection technologies, and relates to a detection circuit for a helicopter alternating current power supply system. The detection circuit is characterized by being composed of a first relay JA, a second relay JB, a first fixed resistor R1, a second fixed resistor R2, an ammeter A, a voltmeter V, diodes P1 and P2, a first reset button switch M1, a second reset button switch M2, a first double-pole double-throw switch K1, a second double-pole double-throw switch K2, a first single-pole single-throw switch K3 and an indicator lamp L1. According to the detection circuit for the helicopter alternating current power supply system, potential safety hazards in the measurement process are eliminated; loading measurement is achieved, and the accuracy of test results is improved; the measurement process is simplified, the measurement period is shortened, and the measurement efficiency is improved.