β-Fe1-xRuxSi2 solid solution was synthesized by solid state reaction at 1100 °C for 48 h and subsequent annealing at 850 °C for 168 h in an evacuated silica tube. Single phase solid solution was obtained in the composition range 0 ≤ x ≤ 0.1. The thermal stability range of the β-phase is extended to higher temperature region by partial substitution of Ru atom. The thermoelectric properties of Cr or Co-doped β-Fe1-xRuxSi2 strongly depend on the sintering conditions. The samples with optimum thermoelectric properties are obtained by high-pressure sintering at 3 GPa and 800 °C for 1 h. The optimum compositions are found to be Fe0.92Ru0.05Cr0.03Si2 and Fe0.92Ru0.05C0.03Si2 for p-type and n-type materials, respectively. The power factors (σα2) of these materials are higher than that of β-FeSi2 based materials.