Nanowire is mainly used in biological sensor because it has the high surface-to-volume ratio. In this study, we have successfully fabricated the N-SiGe nanowire with different Ge concentration by side-wall spacer technique respectively. The 3-amino-propyltrime-thoxy-silane (APTS) was used to modify the surface, which can connect the bio-linker. The conductance of SiGe nanowire increases owing to APTS with positive charge. The bis (sulfosuccinimidyl) suberate sodium (BS3) as the bio-linker connects to APTS, and the conductance decreases because of negative charge. Finally, the protein immunoglobulin G (IGG) is linked to BS3, and the conductance reduces for negative charge. Comparing the conductance change; the SiGe nanowire with higher Ge concentration improved the sensitivity. But the over-higher Ge concentration (40%) did not increase the sensitivity; the reason maybe the higher defect appears at the surface as higher Ge concentration.