Ag1-xPb18SbTe20(x＝0，0.25，0.5，0.75) samples were prepared by melt-quench-spark plasma sintering(SPS). As the Ag content decreased, a second phase Sb2Te3 occurred in samples and the carrier concentration increased to 5×1018cm-3 and then ceased to increase as Ag content decreased further. The carrier mobility decreased first, and then increased, as the Ag content decreased. As temperature increased, the carrier scattering mechanism shifted gradually from ionized impurity scattering to acoustic phonon scattering. As the Ag content decreased, the electric conductivity increased while the Seebeck coefficient decreased, and the thermal conductivity show an increasing trend.