Abstract: Conventional method to fabricate nanobeams by dry etching will induce crystal damage inevitably. A new process method is proposed to fabricate nanobeams without surface damage layer. SiO₂ masks above the middle of silicon beams are modified by Focused ion beam （FIB） after conventional photolithography. After KOH etching,sidewalls with （111） terminations are all vertical to （110） surface plane,based on the material and process properties of crystal silicon. （111） Terminations spread from the middle to the ends of beams along with the ＜112＞ direction by self-modifying etching,until beams are formed. After freeze drying,one silicon nanobeam with width 122nm is obtained on （110） Silicon-On-Insulator （SOI） substrate finally. Self-modifying etching improves the process repeatability. Besides,due to the combination of wet etching and FIB,this presented process method has some merits such as no surface damage,good repeatability,and high processing resolution.