Power　consumption　of　micro-controllers　and　sensor　systems　have　been　greatly　reduced　in　the　last　decade,　new　power　supply　method　such　as　energy　harvesting　is　now　an　alternative　method　to　power　Internet　of　things　(IoT)　devices.　A　few　square　centimeters　sized　thermo-electric　generators　(TEGs)　can　convert　a　few　degrees　Celsius　temperature　gradients　into　milli-watts　of　electric　power.　This　paper　presents　the　design　of　a　TEG　energy　harvesting　powered　LoRa　IoT　device.　The　power　management　circuits　design,　super-capacitor　energy　storage　unit　and　the　IoT　low　power　algorithm　are　introduced.　The　system　demonstrated　the　TEG　power　generation　of　0.4-12　mW,　IoT　device　current　consumption　of　79　mA　in　data　transmission　mode,　less　than　50　μA　in　sleep　mode.　With　super-capacitor　energy　storage　unit,　the　IoT　device　can　be　powered　entirely　from　thermo-electric　energy　without　batteries.　In　addition　to　the　system　implementation,　a　comprehensive　simulation　model　is　created　to　optimize　the　form　factor　of　TEG,　selection　of　the　super-capacitor　and　the　operation　duty　cycles　of　IoT　devices.　©　2019　IEEE.