The invention discloses a power supply line three-phase current transformer secondary loop polarity detection device, and relates to the electrotechnics field; the power supply line three-phase current transformer secondary loop polarity detection device comprises a primary side power supply circuit and a secondary side polarity detection circuit of a three-phase current transformer; the primary side power supply circuit comprises a first DC power supply DC1, a power supply total switch K0, a button switch AN and A-C phase three power supply branches; the power supply total switch K0 is a double-knife-single-throw switch; the A-C phase three power supply branches are same in structures; the A phase power supply branch comprises A-phase primary side binding posts AP1 and AP2 and a first double-knife-single-throw switch K1; the power supply line three-phase current transformer secondary loop polarity detection device uses the detection control and intelligent prompt technologies, so one worker can finish the detection task, thus reducing the original working time of 90 minutes down to 40 minutes, and improving the working efficiency by 55%.