In order to cope with the energy shortage issue, the thermoelectric (TE) materials has attracted growing attention in recent years. The p-type β-Zn4Sb3 has been an ideal candidate for mid-temperature TE generator, as it composes of cost-effective and environmental-friend elements. Nevertheless, its moderate TE conversion efficiency and deficient high-temperature thermal stability have been the major roadblock for the development. Herein, we introduced the IIIA-group (Gallium) dopant into the Zn4Sb3, aiming to improve the TE performance. Meanwhile, the addition of Ga is effective in stabilizing the Zn4Sb3, providing eligible thermal stability at high temperature. The doping strategy is guided by the experimental-determined phase diagram. At 623 K, the maximum solubility of Ga in Zn4Sb3 is less than 4 at.%Ga. Consequently, the Ga-substituted (Zn1-xGax)4Sb3 achieves high figure of merit zT of 1.36 at 673 K, resulting from the reduced κ~0.70 (W/mK) and enhanced PF~1.3 (mW/mk2).