LoRa　is　a　modulation　technology　for　low　power　wide　area　networks　(LPWAN)　with　enormous　potential　in　5G　era.　However,　the　performance　of　LoRa　system　deteriorates　seriously　in　fading-channel　environments.　To　tackle　this　problem,　in　this　paper　we　introduce　multiple-input-multiple-output　(MIMO)　configuration　employing　space-time　block　coding　(STBC)　schemes　into　the　LoRa　system　to　formulate　an　STBC-MIMO　LoRa　system.　Then,　we　investigate　the　theoretical　performance　of　the　proposed　system　over　Rayleigh　fading　channels.　To　this　end,　we　derive　the　distribution　of　the　decision　metric　for　the　demodulator　in　the　proposed　system.　Based　on　the　above　distribution,　we　propose　a　closed-form　approximate　BER　expression　of　the　proposed　system　when　perfect　and　imperfect　channel　state　information　(CSI)　are　considered.　Furthermore,　we　analyze　the　diversity　order　and　the　throughput　of　the　proposed　system.　The　results　of　the　diversity　analysis　demonstrate　that　the　diversity　order　of　the　system　in　the　imperfect　CSI　scenario　with　fixed　channel　estimate　error　variance　is　zero.　However,　in　the　imperfect　CSI　scenario　with　a　decreasing　channel　estimate　error　variance　and　the　perfect　CSI　scenario,　the　system　can　achieve　full　diversity.　In　addition,　the　results　of　the　throughput　analysis　show　that　the　throughput　of　the　proposed　system　is　little　affected　by　CSI　conditions.　Simulation　results　verify　the　accuracy　of　the　theoretical　analysis　and　the　excellent　performance　of　the　proposed　system.　Due　to　such　superiority,　the　proposed　STBC-MIMO　LoRa　system　can　be　considered　as　a　good　scheme　for　LPWAN.