Mg3Sb2 material is an excellent thermoelectric material in the mid-temperature region, with extremely low thermal conductivity, but its carrier concentration is low. In this paper, n-type Mg3.2Y0.05Sb1.5Bi0.05Teδ samples were prepared by mechanical alloying method combined with spark plasma sintering (SPS) technology, and their thermoelectric transport properties were investigated. The results show that the anion site doping element Te can further increase the carrier concentration of the cation site doped Mg3.2Y0.05Sb1.5Bi0.5 material. The carrier concentration is increased from 5.02×1019 to 9.76×1019 cm-3, and the power factor is also improved from 10.89 to 15 μW·K-2·cm-1. In addition, after Te element enters the lattice, the crystal thermal conductivity of the material is also greatly reduced, from 0.92 to 0.68 W·m-1·K-1. The sample with the highest carrier concentration has a peak zT of 1.6 at 750 K, and an average zT of 1.0 in the temperature range of 300-750 K. This work proves that the co-doping of cations and anions is better than single-cation or single-anion doping for increasing the carrier concentration of Mg3Sb1.5Bi0.5. This doping method is expected to be applied to the optimization of other thermoelectric materials.