Abstract: It was found that in an acetate buffer medium of pH 3.8, Fe(Ⅲ) ion was reduced to Fe(Ⅱ) ion by clindamycin phosphate (CLP) which in turn reacted with o-phenanthroline solution to form a colored complex (λmax=508 nm) and that linear relationship was kept between values of absorbance and mass concentration of CLP ［calculated indirectly from the amount of Fe(Ⅱ) ion found］ in the range of 0.70-140 mg·L-1. Based on this fact and by applying the FIA technique, an indirect FI-spectrophotometric method for determination of CLP was proposed. The optimum analytical conditions found were as follows: ① amount of the acetate buffer solution added: 2.5 mL; ② mass concentration of Fe(Ⅲ) solution: 10.0 mg·L-1; ③ concentration of o-phenanthroline solution: 1.5×10-3mol·L-1; ④ temperature of reaction: 85 ℃. Detection limit (3s/k) of the method found was 0.060 mg·L-1. The proposed method was applied to determination of CLP in drug samples, giving results in consistency with those found by the method of national standard of drugs.