A series of high-textured Ag-doped or/and Ag-added Ca 3 Co 4 O 9 ceramic specimens have been prepared by a cold-pressing technique and their thermoelectric properties were compared from room temperature to 1000K. The substitution of Ag + for Ca 2+ causes the reduction of resistivity and the enhancement of thermoelectric power simultaneously, whereas the addition of metal Ag results in the decrease on resistivity together with thermoelectric power. Both Ag + doping and Ag addition can enhance power factor; however, the doping of Ag + is advantageous for the suppression of thermal conductivity whereas the addition of Ag facilitates thermal conductivity. Ca 2.7 Ag 0.3 Co 4 O 9 /Ag-10wt% composite exhibits a quite respectable thermoelectric performance; the dimensionless figure of merit ZT can reach 0.5 at 1000K.