Abstract: The patterned Si nanowire arrays as photoanode for photoelectrochemical cells have been successfully fabricated by combining photolithography and by metal-assisted Si chemical etching and energy-conversion properties are investigated.The morphology of Si nanowire arrays is characterized by scanning electron microscopy and anti-reflection property is characterized by hemispherical reflectance spectra.The reflectance of Si nanowire arrays is lower than 5% over the range of 300–1000 nm.The Si nanowire photoelectrochemical cells exhibit a power conversion efficiency of 0.33%.By analyzing the process of photovoltaic conversion,the low conversion efficiency may be attributed to photo-carrier recombination in interface of solid/liquid.