The absorption spectral characteristics and colour range of pigment in Nanyang grey wheat was studied, which provided reference for scientific utilization and development of the pigment. Nanyang grey wheat was soaked in acidic ethanol to extract pigment by ultrasonic. The pigment was determined by acid- base titration and spectrophotometry. The results showed that in the visible region the maximum absorption wavelength lied at 541 nm, colour range was pH 4.75~6.58. The pigment in grey wheat is a relatively ideal, economical and environmentally friendly acid-base indicator, it can be developed and used as a natural colorant and antioxidant in food.