Abstract: With the deepening reform of power electronics, the harmonic problem of new power system is becoming more and more obvious. Under operating conditions, the voltage acting on the bushing insulation contains a large number of high-order harmonics. The additional loss caused by harmonics will aggravate the bushing heating and seriously threaten the safe operation of bushing. In order to study the dielectric loss characteristics of bushing capacitor core under harmonic voltage, taking oil paper capacitive bushing as the research object, the calculation model of bushing dielectric loss under harmonic voltage is deduced theoretically; Through the artificial damp simulation test and dielectric response test, the frequency domain dielectric spectrum of bushing under different damp degree is obtained; and the dielectric loss is calculated. The effects of temperature and moisture on the bushing dielectric loss under harmonic are analyzed.