Rainfall　infiltration　is　one　of　the　main　triggers　of　slope　failure.　Based　on　the　upper　bound　theorem　of　limit　analysis,　this　work　presents　an　analytical　stability　analysis　of　a　3D　vertical　cut　slope　subjected　to　rainfall　infiltration.　An　analytical　model　that　can　directly　provide　pore　water　pressure　change　at　any　depth　and　time　is　adopted　to　calculate　the　time-dependent　matric　suction　and　shear　strength　of　unsaturated　soil　during　the　rainfall　infiltration　process.　Thereafter,　based　on　a　3D　rotational　failure　mechanism　of　a　slope,　the　energy　balance　equation　is　built,　and　the　factor　of　safety　(FoS)　of　the　slope　is　consequently　determined　in　conjunction　with　the　strength　reduction　technique.　The　influences　of　the　3D　characteristics　of　the　slope　and　rainfall　patterns　on　both　FoS　and　failure　pattern　of　the　slope　are　investigated.　It　is　found　that　the　3D　characteristic　of　slope　is　a　key　factor　which　determines　the　FoS　of　slope.　Different　rainfall　infiltration　patterns　lead　to　diverse　variation　rules　of　both　the　FoS　solutions　and　the　critical　failure　patterns　of　slope.　However,　these　rainfall　patterns　with　a　same　accumulated　rainfall　result　in　the　same　FoS　solution　of　slope　at　the　end　of　rainfall　infiltration.　The　present　work　may　provide　guidance　on　the　stability　analysis　and　preliminary　design　of　slopes　subjected　to　rainfall　infiltration.