In this thesis, we successfully designed and fabricated optical high sensitive sensor using silicon nanopillars array by low-cost self-assembly nanosphere lithography method to generate high aspect ratio silicon nanopillars by reactive ion etching and photo-assisted electrochemical etching. In the demonstration of the experimentation, small bio-molecules can be judged by monitoring the polarization variation. We distinguish the bio-molecules from the slight different changes of refractive index, which caused sensor strongly polarization variation, and observe signal constellation by Poincar? sphere based on Polarization Shift Keying (PolSK) fiber-optic system, which makes the sensors extremely sensitive to the refractive index slightly changed resulting from the infiltration of bio-molecules. This is a very promising value from this preliminary experiment. We believe this novel sensor using Si nanopillars array based on PolSK fiber-optic system technology can bring revolutionary medical treatment to the mankind.