The galvanic wet etching was adopted to fabricate single-crystalline Si nanowires (NWs) at room temperature in HF/AgNO3 solution. The focus-ion-beam (FIB) direct-write technology was employed to connect the Si NW and Cr/Au electrode. The microstructure and morphology was studied in details, it demonstrates that the amorphization of Si NWs due to the irradiation of focused Ga ion beams. Temperature dependence of conductivity of an individual Si NW is investigated at the temperature ranges from t05K to 390K. The Mott's variable-range hopping (Mott-VRH) model is applied to the conduction due to disorder effect caused by FIB-Pt. Mott's parameters of Si NWs, such as hopping energy, hopping distance and density of states have been estimated.