In the power system, power capacitors play the role of reactive power compensation, filtering, carrier wave, and high-frequency protection. With the rapid development of the power system towards the "dual high" characteristic, the voltage signal applied to the power capacitor contains a large amount of harmonic voltage, which exacerbates the uneven distribution of voltage and current signals on the capacitor plate. The heating and aging of power capacitors are closely related to their active power losses. Therefore, considering metal and dielectric losses, a wide-band distributed parameter equivalent model of capacitors under harmonic voltage is proposed. The voltage and current distribution characteristics and loss analytical expressions are derived, and calculations are carried out to analyze and summarize the law: under harmonic voltage, the current flowing through the capacitor plates increases, The metal loss and dielectric loss of the electrode plate have significantly increased, presenting an uneven distribution. The loss generates heat, which affects the insulation and operating status of the capacitor.