Organic　thermoelectric　(OTE)　materials　promise　convenient　energy　conversion　between　heat　gradients　and　voltage　with　flexible　and　wearable　power-supplying　devices　at　a　low　price.　Although　a　variety　of　OTE　materials　are　investigated,　the　TE　performance　is　still　far　from　practical　application.　To　achieve　high　TE　performance,　a　thorough　understanding　of　the　structure-property　relationship　in　OTE　materials　is　necessary.　In　this　comprehensive　review,　the　fundamentals　of　OTEs　are　summarized,　the　recent　achievements　of　OTE　materials　are　reviewed,　and　the　relationship　between　structure　and　properties　in　high-performance　OTE　materials　is　discussed.　Furthermore,　how　the　molecular　backbones,　side　chains,　energy　levels,　molecular　packing,　and　heteroatom　effect　all　play　vital　roles　in　thermoelectric　properties　is　addressed.　Finally,　the　future　direction　of　research　on　OTE　materials　is　envisaged.