The invention discloses an alternating-current electric wrench, which comprises a shell, a power unit, a universal motor, an ordinary gear train speed reducer, a planetary gear train speed reducer, a wrench body, a sensor, an information processor and a display device. The universal motor is disposed in the shell and connected with the power unit, the ordinary gear train speed reducer is driven by the universal motor and connected to the shell, and the wrench body is connected with the planetary gear train speed reducer which is driven by the ordinary gear train speed reducer. The sensor is used for measuring rotating speed of the universal motor, the information processor comprises a torque computing module, a memory module and a control module, the torque computing module is connected with the sensor and the display module, the memory module is provided with a preset reference current value, the control module is used for measuring a practical current value of the universal motor and comparing the practical current value with the reference current value, and the control module controls the universal motor to stop rotating when the practical current value is larger than the reference current value. The alternating-current electric wrench is capable of providing larger torsion, and the torque value can be set according to mounting requirements.