Large-area silicon nanowire arrays (SiNWs) were prepared by etching silicon substrate in HF/AgNO3 system solution at near room temperature. Morphology of SiNWs was characterized by scanning electron microscopy. The results showed that morphology of SiNWs could be influenced by solution ratio, temperature and reaction time in the hydrothermal system. The length of SiNWs was about 30-40 μm, and the diameter of SiNWs was in the range of 100-300 nm. SiNWs owned strong optical absorption capacity and could be used for application in solar cell.