The　development　of　efficient　all　perovskite　tandem　solar　cells　has　faced　challenges　related　to　current　matching　and　optical　losses.　In　this　work,　a　design　of　a　non-coplanar　three-terminal　(3T)　all　perovskite　tandem　solar　cell　is　presented,　which　consists　of　a　p-i-n　inverted　NiOX-based　CsPbI2Br　perovskite　top　cell,　and　a　FA(0.6)MA(0.4)Sn(0.5)Pb(0.5)I(3)　perovskite　bottom　cell　with　back-contact　(BC)　device　structure.　It　effectively　mitigated　the　optical　losses　introduced　in　non-absorbing　layers　and　resulted　in　a　2.9%　absolute　efficiency　improvement　compared　to　that　of　planar　sandwich-type　3T　tandems.　Both　optical　and　electrical　characteristics　of　the　multi-terminal　tandem　cells　are　investigated.　Then,　it　is　focused　on　understanding　the　impact　of　top　cell　thickness　on　overall　non-coplanar　BC　3T-tandem　performance,　considering　low-energy　photon　optical　reflection　and　carrier　transport　distance.　Following　optimizations　of　energy　level　and　device　structure,　an　efficiency　of　32.16%　is　achieved,　with　non-coplanar　BC　3T　device　architecture:　top　cell　consisting　of　hole　extraction　layer　(ITO/NiOx),　CsPbI2Br　absorber　layer,　and　electron　extraction　layer　(ZnO/FA(0.6)MA(0.4)Sn(0.5)Pb(0.5)I(3)/SnO2/Ag);　and　bottom　cell　(Ni/NiOx/FA(0.6)MA(0.4)Sn(0.5)Pb(0.5)I(3)/SnO2/Ag);　bottom　perovskite　layer　has　two　functions,　one　is　electron　transport　layer　for　top　cell,　and　the　other　is　low-energy　photon　absorption　layer　in　bottom　cell.　It　provides　insight　and　a　promising　pathway　for　manufacturing　high-efficient　all　perovskite　tandem　solar　cells.