A dynamic chemical etching method based on siphon principle has been developed for controllable fabrication of fiber nano-tips, which could be used in near-field optical microscope and optical nanosensors. Compared with traditional static chemical etching, this method has advantages such as reproducibility, controllability, convenience, less cost, and making tip surface smooth. The overall shape and the tape angle of the tip can be effectively controlled through the speed and direction of water flux. Tips with taper angles from 20degrees to 55degrees, and tips with double tapers have been achieved by this method. (C) 2004 American Vacuum Society.