The invention discloses a capacitor and a mass determination method of a mass resonance plate and relates to the electric power equipment technology field. The capacitor comprises a capacitor shell and a capacitor core installed in the shell. The mass resonance plate is arranged in the capacitor core. Density of the mass resonance plate is greater than a density threshold, a distance from the massresonance plate to one end of the capacitor core is a first distance, the first distance is determined according to a mass of the mass resonance plate, and the mass of the mass resonance plate is determined according to an inherent frequency of the capacitor and an electric field force frequency of the capacitor. The capacitor of the invention can eliminate resonance between the inherent frequency of the capacitor and the electric field force frequency so as to reduce a noise of the capacitor.