Abstract: In an acetate buffer medium of pH 3.85, Fe(Ⅲ) was reduced by pyritinol hydrochloride to give Fe(Ⅱ), and a colored complex was formed by its reaction with o-phenanthroline, having its absorption maximum at the wavelength of 508 nm. Based on these facts, the determination of pyritinol hydrochloride by stopped flow injection (FI)-spectrophotometry was proposed. Linear relationship between values of ΔA and mass concentration of pyritinol hydrochloride was kept in the range of 8.00-500 mg·L-1, and detection limit (3s/k) of the method found was 1.54 mg·L-1. The proposed method was used in the determination of pyritinol hydrochloride in its drugs, and values of recovery found were in the range of 99.6%-100% with RSD (n=6) less than 2%.