A reaction between Moxifloxacin HCl and FeCl3 solution in slightly acidic medium was studied. It gave brown colour complex having maximum absorbance at 407.0nm. The reaction is selective for Moxifloxacin HCl with 0.00024µg/uL and different concentration of FeCl3 was applied.  The color reaction obeyed Beer’s law from 0.01 µg /µL to 0.00018 µg/µL of FeCl3 solution having concentration 0.1ug∕uL and relative standard deviation 0.026%.The quantitative estimation of moxifloxacin HCl in blood sample is also studied. Key Words: Moxifloxacin, UV-Visible Spectrophotometer, Ferric Chloride, Beer’s law, Color reaction, Analytical method