A hierarchical roughness surface with micro-and nano-structures was fabricated on mild steel by chemical etching with a mixture acid (2%HNO3 + 6%H2SO4 + 6%H3PO3) solution. The surface was modified by fluoroalkylsilane. The wettability of the modified surfaces was studied by contact angle method and Electrochemical Impedance Spectroscopy (EIS), and their morphology was investigated by Scanning Electron Microscopy (SEM). The roughness of the steel etched consisted of fine micro-steps in grains. The treated surface exhibited super-hydrophobic properties, water contact angle is high to 152° after modification for 6 min at room temperature. The results indicated that with the increase of etching time, the hierarchical structure gradually formed on the surface and the contact angle gradually decreased.