(Ag,Sn)　co-doped　Cu3SbSe4　nanocrystals　are　obtained　via　a　facile　microwave-assisted　solvothermal　method,　and　their　thermoelectric　properties　are　investigated　in　the　temperature　range　from　300　K　to　623　K.　Sn-doping　on　Sb　sites　dramatically　increases　the　carrier　concentration　and　thus　the　electrical　conductivity,　promoting　the　thermoelectric　power　factor.　Further　alloying　with　Ag　on　Cu　sites　strongly　suppresses　the　lattice　thermal　conductivity　close　to　the　glass　limit.　Aside　from　point　defect　scattering,　such　reduction　in　lattice　thermal　conductivity　largely　relies　on　the　formation　of　Cu2-xSe　nanoinclusions,　which　serve　as　additional　scattering　centers　for　phonons.　Overall,　the　sample　with　the　nominal　composition　of　Cu2.8Ag0.2Sb0.95Sn0.05Se4　reaches　a　minimum　lattice　thermal　conductivity　of　0.27　W　m(-1)　K-1　and　a　maximum　zT　of　1.18　at　623　K,　which　is　the　best　result　for　the　Cu3SbSe4-based　materials　in　the　same　temperature　region.　Our　results　demonstrate　that　the　microwave-assisted　synthesis　method　is　capable　of　fabricating　Cu　based　ternary　compounds　with　high　thermoelectric　performance.