The invention belongs to the industrial measurement and control field, relates to a three-phase alternating-voltage high-precision fast detection circuit based on a transformer and is suitable for allkinds of application occasions where high-precision real-time monitoring and control are performed on an effective value of a three-phase alternating voltage. The circuit includes a three-phase voltage transformer VS1, an A-phase positive operational amplifier IC1, a B-phase positive operational amplifier IC2, a C-phase positive operational amplifier IC3, an A-phase negative operational amplifierIC4, a B-phase negative operational amplifier IC5, a C-phase negative operational amplifier IC6, an output operational amplifier IC7, an A-phase positive diode D1, a B-phase positive diode D2, a C-phase positive diode D3, an A-phase negative diode D4, a B-phase negative diode D5, a C-phase negative diode D6 and the like. The circuit consists of a three-phase bridge-type super diode rectifying circuit and an alternating voltage signal processing circuit, and can detect an effective value signal of the three-phase alternating voltage in high precision, wide range and real-time modes. The circuit is simple, has low cost, high reliability and good versatility, and is easy to form productization.