Nonstoichiometric AgSbTe2+x (x=0—0.05) compounds have been prepared by combining melting-quench and spark plasma sintering. The effects of excessive Te on thermoelectric properties were investigated at 300 K to 600 K. Results indicated that the concentration of Ag+ ion vacancy, hole concentration and electrical conductivity increase remarkably with the increasing amount of Te, while the Seebeck coefficient decreases. In addition, the total thermal conductivity of the samples increases slightly as Te content increases. The lattice thermal conductivities of nonstoichiometric samples range from 0.32 to 0.49 W/mK, which are less than the value of the stoichiometric sample, and close to the theoretical minimum thermal conductivity. For AgSbTe2.01 (x=0.01), a maximum figure of merit ZT=1.41 was obtained at 562K. This value is 15% higher than that of the stoichiometric sample.