Abstract: High voltage inverter is widely used in the auxiliary power system of power plant. The harmonic current generated by the rectifier link at the input side will cause the voltage distortion of the auxiliary bus, so that the parallel compensation capacitor bank can withstand the superposition of harmonic current and overvoltage, and then induce overheating failure. Based on the mechanism of harmonic generation, this paper establishes the dielectric heat loss model of capacitor bank under harmonic environment, analyzes the influence of harmonic amplification effect on capacitor temperature rise and insulation aging, and quantitatively evaluates the harmonic treatment scheme combined with simulation and engineering measured data, so as to provide theoretical basis and engineering reference for the safe operation of capacitor bank in auxiliary power system.