Doping-and alloying-induced point defects lead to mass and strain field fluctuations which can be used as effective strategies to decrease the lattice thermal conductivity and consequently boost the performance of thermoelectric materials.Herein,we report the effects of Sm and S co-doping on thermoelectric transport properties of copper antimony selenides in the temperature range of 300 K ＜ T ＜ 650 K.Through the Callaway model,it demonstrates that Sm and S co-doping induces strong mass differences and strain field fluctuations in Cu3SbSe4.The results prove that doping with suitable elements can increase point defect scattering of heat-carrying phonons,leading to a lower thermal conductivity and a better thermoelectric performance.The highest figure of merit (ZT) of ～ 0.55 at 648 K is obtained for the Sm and S co-doped sample with nominal composition of Cu2.995Sm0.005SbSe3.95S0.05,which is about 55％ increase compared to the ZT of pristine Cu3SbSe4.