In this research study we have targeted to fabricate a tapered optical fiber coated with zinc oxide doped with KCl to improve the humidity sensing capability of zinc oxide. The optical fiber was tapered through chemical etching method by HF acid (49.5%). The nano-crystalline Zinc Oxide (ZnO) was synthesized using single molecular precursor method doped with KCl. The resulting material was characterized with Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). The sensing mechanism of this sensor is based on the change of the optical properties of the coating when the relative humidity increases. The humidity sensing characteristic has been estimated by measuring the Optical Permeability (OP) as a function of percentage of Relative Humidity (%RH) in the ranging from 5 to 98% inside a closed chamber. The tapered optical fiber tested with an overlay coating at the optimal working point achieves better sensitivity. The experimental results show that the 5.7 wt% KCl doped ZnO nano-fibers hold super-rapid response and recovery than normal ZnO coating.