Silicon (Si) nanopartilces which studied are in the size range (7 – 23 nm) have been synthesized by mechanical milling. The milled powder was etched by HF & CH3COOH acids. The size, structural, and optical characterization of these nanoparticles were determined by X-ray diffraction(XRD),Atomicforce microscopy (AFM),Fourier transform infrared spectroscopy (FTIR) and UV-VIS spectroscopy. The result confirmed that Si isnanoparticles in crystal phase with band gap 3.15eV, due to the effect of quantum confinement. This technique has been shown to have an advantage over other methods of producing nanoparticles because of low cost, small particles size, low agglomeration, narrow size distributions and uniformity of crystal structure and morphology