The efficiency-upgrading role that La0.8Sr_(0.2)CoO_3(LSCO) plays in the thermoelectric properties of Bi Cu Se O(BCSO) has been studied. LSCO was introduced into BCSO, increasing the electrical conductivity from 3.3 to 52.3 S cm-1 at 303 K, from 35.8 to 97.3 S cm~(-1) at 873 K; respectively. The Seebeck coefficient of all composites still holds around or more than 200 μV/K. Based on the enhanced electrical conductivity and high Seebeck coefficient, the power factor is enhanced by approximately 35%, with the best sample reaching a maximum value of 476.7 μ Wm~(-1) K~(-2) at 873 K. The lattice thermal conductivity of the nanocomposites is reduced as LSCO content increases from 15 vol% to 30 vol% due to the phonon scattering by nanoparticles and grain boundaries, resulting in a significant reduction in total thermal conductivity. In short, the enhanced thermoelectric figure of merit of 0.67 at 873 K for the sample containing 20 vol% LSCO as compared to 0.53 for the pure sample; announces the promising effect of LSCO on improving thermoelectric properties of Bi Cu Se O. The efficiency-upgrading role that La0.8Sr_ (0.2) CoO_3 (LSCO) plays a role in the thermoelectric properties of Bi Cu Se O (BCSO) has been studied. LSCO was introduced into BCSO, increasing the electrical conductivity from 3.3 to 52.3 S cm- 1 at 303 K, from 35.8 to 97.3 S cm -1 at 873 K; respectively. The Seebeck coefficient of all composites still holds around more than 200 μV / K. Based on the enhanced electrical conductivity and high Seebeck coefficient, the power factor is enhanced by approximately 35%, with the best sample reaching a maximum value of 476.7 μ Wm -1 K -2 (at) 873 K. The lattice thermal conductivity of the nanocomposites is reduced as LSCO content increases from short to high, from 15 vol% to 30 vol% due to the phonon scattering by nanoparticles and grain boundaries, resulting in a significant reduction in total thermal conductivity. In short, the enhanced thermoelectric figure of merit of 0.67 at 873 K for the sample containing 20 vol% LSCO as compared to 0.53 for the pure sample; announces the promising effect of LSCO on improving thermoelectric properties of Bi Cu Se O.