The effects of the dopant (Mn) ratio on the microstructure and thermoelectric properties of $FeSi_2$ alloy were studied in this research. The alloy was fabricated by a combination process of ball milling and high pressure pressing. Structural behavior of the sintered bulks were systematically investigated by XRD, SEM, and optical microscopy. With increasing dopan (Mn) ratio, the density and ${varepsilon}-FeSi$ phase of the sintered bulks increased and maximum density of 94% was obtained in the 0.07% Mn-doped alloy. The sintered bulks showed fine microstructure of ${alpha}-Fe_{2}Si_{5}$, ${varepsilon}-FeSi$ and ${eta}-FeSi_2$ phase. The semiconducting phase of ${eta}-FeSi_2$ was transformed from ${alpha}-Fe_{2}Si_{5}+{varepsilon}-FeSi$ phase by annealing.