A light fixture abnormal condition detection system comprises a power supply circuit, a detection circuit and a protection circuit; the power supply circuit comprises 220AC, a transformer W1 and a rectifier bridge T; the detection circuit comprises a transformer W2, a diode D1 and a resistor R1; the protection circuit comprises a relay J1, a relay J2, a diode potentiometer RP1 and a one-way thyristor RT1. The novel detection system circuit discards a complex chip structure, and electronic elements can be simplify combined so as to carry out detection protection for overvoltage, overcurrent and undervoltage conditions of the light fixture circuit, thus simplifying the circuit structure, improving interference immunity, so the circuit is low in making cost, strong in interference immunity and various in functions.