Abstract N-type Mg2Si0.58Sn0.42 − xBix (0 ≤ x ≤ 0.015) compounds were prepared by melting the element metals in sealed tantalum tubes followed by hot pressing. The XRD results indicate that all samples are composites containing both major magnesium silicide solution phase and minor magnesium stannide solution phase. The Hall measurements show that the carrier concentrations and electrical conductivities increase with the increase of Bi doping amount. It was found that the intrinsic excitation shifts to high temperature due to Bi doping, which leads to the increase of the peak-temperatures of the Seebeck coefficient. The maximum dimensionless figure of merit is 0.65 at 700 K for the sample x = 0.015.