Abstract: Diffuse reflectance FTIR spectroscopy was applied to the determination of vitamin C in injections. Diluted injection liquor was directly injected into the matrix of KBr, which was then dried, ground and sieved successively. The absorption peak of C=O stretching at 1 702 cm-1 was selected for quantitative analysis. Absorbance in terms of peak area was measured in the region of wave numbers 1 685-1 736 cm-1. Sodium ascorbate was used as standard substance. Linearity range of sodium ascorbate was found between 0.2%-2.0% with detection limit (3s/k) of 0.64 mg·g-1. The proposed method was applied to the analysis of vitamin C injections, giving results in consistency with the values obtained by iodometric method. Values of RSD′s (n=10) found were in the range of 1.9%-2.5%.