Long-term　accelerated　aging　test　of　generator　stator　insulation　in　the　laboratory　was　conducted.　Nondestructive　parameters,　such　as　dissipation　factor　(tan　delta),　capacitance　(C)　and　the　voltage　(U-i2)　at　which　the　current　increases　abruptly,　were　measured　in　the　period　of　aging　test.　The　breakdown　test　was　performed　to　determine　residual　breakdown　voltage　(BDV).　The　correlation　coefficients　between　BDV　and　nondestructive　parameters　were　compared,　The　most　effective　parameter　to　describe　the　aging　condition　of　the　stator　insulation　was　U-i2.　In　this　paper,　the　relationship　between　BDV　and　nondestructive　parameters　was　analyzed　theoretically.