In　this　study,　we　perform　a　stability　analysis　on　three-dimensional　(3D)　geosynthetic-reinforced　soil　structures　(GRSSs),　focusing　on　their　response　to　varying　rainfall　conditions.　The　magnitude　and　distribution　of　pore　water　pressure　in　unsaturated　backfills　throughout　the　infiltration　event　is　calculated　to　determine　the　time-dependent　matric　suction　and　apparent　cohesion　in　backfills.　An　analytical　expression　representing　the　necessary　strength　for　geosynthetic　reinforcement　in　3D　GRSS　is　derived　from　the　energy　balance　equation,　utilizing　the　kinematic　limit　analysis　approach.　The　validities　of　both　the　necessary　reinforcement　strength　and　the　pore　water　pressure　distribution　are　confirmed　in　this　study.　Further　exploration　is　conducted　into　the　effects　of　the　3D　geometric　features　of　the　GRSSs,　the　effective　cohesion　and　friction　angle　of　backfills,　alongside　factors　related　to　rainfall　intensity,　duration　and　patterns.　These　considerations　influence　both　the　required　reinforcement　strength　and　the　failure　pattern　of　the　GRSSs.　The　findings　indicate　that　the　necessary　reinforcement　strength　and　critical　failure　pattern　of　a　GRSS　are　dictated　not　only　by　its　3D　geometric　properties　but　also　by　the　unsaturated　soil　mechanics　and　the　nature　of　the　rainfall　it　encounters.　An　identical　accumulated　rainfall　will　result　in　approximately　a　same　required　reinforcement　strength　solution　of　GRSS　after　rainfall.　This　study　provides　guidance　on　preliminary　design　of　GRSSs　under　rainfall　conditions.