With the fascinating properties observed in high entropy alloys, the idea of high entropy design has been applied to many material fields. Thermoelectric materials have some particular requirements for high entropy structure according to their transport characteristics. Here, we revealed that the high entropy structure for thermoelectrics required less lattice distortion, and the doping sites should have less influence on the Fermi surface. In the designed compound of Cu_0.8Ag_0.2Zn_0.1Ga_0.4Ge_0.1In_0.4Te₂, the room-temperature thermal conductivity is reduced by 80% as compared to the matrix, and the maximum ZT is enhanced to 1.02. In SnTe, the solid solution of AgSbSe₂ reduces the room-temperature thermal conductivity by 80%, reaching 1.3 W·m^-1·K^-1. This study shows that the high entropy structure following the proposed designing rules could be an important strategy for thermoelectrics.