When　corona　or　glow　discharge　occurs　before　the　breakdown　in　air　gap,　air　humidity　may　affect　the　AC　breakdown　voltage.　However,　the　parameters　ranges　of　the　influenced　electrode　structure　are　not　clear.　In　order　to　further　reveal　the　influence　of　air　humidity　on　the　breakdown　characteristics　of　short　gaps　under　non-uniform　AC　electric　fields,　the　AC　breakdown　tests　were　carried　out　with　the　interelectrode　gap　distance　of　1~5　cm　and　the　high　voltage　electrode　radius　of　0.1~2　cm.　The　results　show　that,　within　the　given　parameters　of　the　electrode　structure　when　the　electrode　radius　is　larger　than　0.5　cm,　the　humidity　has　a　negligible　effect　on　the　breakdown　voltage.　When　the　electrode　radius　is　less　than　0.5　cm,　the　humidity　will　affect　the　breakdown　voltage,　especially　under　longer　gap　distances.　When　the　electrode　radius　is　0.3　cm,　the　influence　of　the　humidity　is　the　most　significant.　Combined　with　the　analyses　of　the　hybrid　breakdown　criterion,　the　streamer　breakdown　criterion　is　still　effective　when　the　geometric　structure　parameter　is　larger　than　the　critical　value,　but　the　breakdown　field　formula　should　be　corrected　in　partial　regions　with　the　humidity　being　considered.　The　results　can　provide　a　reference　for　the　insulating　design　of　non-uniform　air-insulated　gaps.　©　2019,　High　Voltage　Engineering　Editorial　Department　of　CEPRI.　All　right　reserved.