High　voltage　XLPE　power　cable　is　a　very　important　part　of　power　system.　The　degree　of　electric-tree　aging　in　the　cable　can　be　estimated　effectually　by　measuring　partial　discharge.　An　on-line　partial　discharge　monitor　system　of　XLPE　power　cable　was　developed　based　on　the　virtual　instrument　designing　conception.　This　system　has　the　advantage　of　wide　analog　bandwidth,　excellent　anti-interference　ability,　good　stability,　powerful　analysis,　friendly　interface,　convenient　operation,　etc,　it　can　detect　the　quantity　of　partial　discharge　(PD)　in　XLPE　power　cable.　It　holds　utility　value　in　power　system.