How to rapidly determine synthesized pigments or dyes adulterated in natural pigments is a difficult problem for food analysts. Natural paprika red is widely used in foods because of its coloration and pharmaceutical effect, but it is sometimes adulterated with Sudan dyes for its poor stability under light or heat treatment. In the present paper, the macro-fingerprint characteristic of infrared spectroscopy was utilized to identify Sudan dyes adulterated in paprika red. The strong peaks at 1 621, 1 500 and 751 cm-1 in FTIR spectra and at the fingerprint region of 753, 684 and 496 cm-1 in the secondary deriative FTIR spectra were remarkable characteristics for Sudan dyes adulterated in paprika red, of which the limit of determination was about 1%.