The invention provides a device for inhibiting harmonic amplification on third winding side of an ultrahigh voltage transformer, comprising four groups of parallel capacitors, wherein each group comprises three capacitors and three reactors; each capacitor is in series connection with the reactor; three capacitors in each group have identical capacity; and three reactors in each group have identical capacity; the capacity of all capacitors in four parallel capacitors have identical capacity; for four parallel capacitors, each reactor in two groups is the first capacity, while the reactors in the other groups are the second capacity, namely reactors with two capacities are used for mixed arrangement. Compared with the prior art of using reactors with one capacity on the third winding side of the ultrahigh voltage transformer, the invention can inhibit harmonic amplification on the third winding side of the ultrahigh voltage transformer.