Abstract: This paper investigated the effects of Sr doping on the phase and thermoelelctric properties of layered cobalt oxides Bi₂Ca₂Co₂O_y, which has shown promising potential for waste heat recovery. After synthesized of Bi₂Ca₂Co₂O_y by solid-state reaction method, it was ball milled into power and followed by cold pressing into disk and sintering in air. The phase of the fabricated disk sample was checked by XRD, and the thermoelectric properties were measured by LFA-457 and ZEM-3 from room temperature to 973 K. The results show that with the part substitution of Ca atom by Sr atom, both the electrical resistivity and the thermal conductivity were reduced with little effects on the Seebeck coefficient. This results in the power factor increase and the optimization of thermoelectric figure-of-merit ZT.