The　saturated　hydraulic　conductivity　is　inherently　variable.　An　extension　infiltration　model　considering　the　variability　of　saturated　hydraulic　conductivity　is　established　using　the　classic　Green-Ampt　model;　and　then　the　corresponding　depth　of　the　wetting　front　and　the　distribution　of　water　content　are　determined.　Meanwhile,　a　closed　form　of　the　limit　state　function　is　presented,　based　on　the　combination　of　the　extension　of　the　Green-Ampt　model　and　the　infinite　slope　stability　model.　Random　number　sequences　of　saturated　hydraulic　conductivity　are　generated　following　a　lognormal　distribution　using　the　Monte　Carlo　simulation　method.　For　a　hypothetical　slope　that　is　subjected　to　steady-state　rainfall　infiltration,　a　series　of　parameter　analyses　is　conducted.　The　results　show　that　the　cases　with　a　smaller　coefficient　of　variability　have　a　smaller　failure　probability　in　the　initial　stage　of　rainfall　infiltration.　However,　as　rainfall　progresses,　the　cases　with　a　smaller　coefficient　of　variability　have　a　larger　probability　of　failure　instead.　The　most　likely　failure　time　of　the　slope　is　not　affected　by　the　coefficient　of　variability,　but　depends　on　the　intensity　of　rainfall.　The　corresponding　probability　of　the　most　likely　failure　time　decreases　with　the　increase　of　the　variability.　©　2016,　Academia　Sinica.　All　right　reserved.