The utility model discloses a secondary alternating-current harmonic eliminating device for an electromagnetic voltage transformer. The secondary alternating-current harmonic eliminating device comprises a full-control switch unit (1) and a discharging resistor (2). The full-control switch unit (1) and the discharging resistor (2) are connected in series and connected with the two ends of an open triangular winding (3) of the electromagnetic voltage transformer to form a circuit. The full-control switch unit (1) is composed of two full-control switch devices connected reversely in parallel. Insulated gate bipolar transitors (IGBT) or integrated gate commutated thyristors (IGCT) or gate turn-off ohyristors (GTO) are adopted as the full-control switch devices. The secondary alternating-current harmonic eliminating device is simple in structure, ferromagnetic resonance overvoltages generated by the electromagnetic voltage transformer can be effectively restrained, meanwhile, the normal and asymmetric running mode of a system cannot be influenced, and therefore safety and stability of power system running are effectively improved.