The invention discloses a power cable partial discharge detecting device based on multiples of stages of power sources and series resonance and an evaluation method. The detecting device comprises a voltage source unit, an electric reactor unit, a measuring unit and a host system; multiples of stages of modular power sources are connected in series and parallel so as to form the voltage source unit; the number of the stages of output ends which are connected in series and the number of the stages of output ends which are connected in parallel are controlled, so that the output voltage and capacity of the inversion power sources can be easily controlled; the output ends are connected in series, so that the output voltage can be significantly increased; the output ends can be connected in parallel, so that output power can be significantly increased; each modular power source includes an inversion unit, a power supply unit, an excitation transformer, a power electronic switch unit, a high-voltage semiconductor switch unit, and a control unit; and the voltage source unit is used for outputting frequency-adjustable sine waves. According to the detecting device of the invention, noise interferences generated by the inversion modules can be eliminated through the power electronic switch units, and therefore, the accurate detection of partial discharge can be realized. The detecting device has a wide application range.