Perovskite manganites CaMn1-y W (y) O-3 (0 a parts per thousand currency sign y a parts per thousand currency sign 0.05) were synthesized using solid-state reaction technique. The influence of W doping on the structure, charge carrier transports and phonon scattering of CaMnO3 was investigated. Doping was found to increase the carrier concentration, leading to enhanced electrical conductivity and decreased Seebeck coefficient. In addition, it decreased the thermal conductivity of CaMnO3, which was believed to associate with decreased phonon mean path and doping-induced MnO6 octahedral distortion, as evidenced by the increased orthorhombicity. A twofold increase of figure of merit (ZT) of 0.15 at 973 K was observed in CaMn0.99W0.01O3, compared with the undoped CaMnO3.