Abstract: Within the common food pH range, the effect of pH on the color and UV-Vis absorption spectra of purple sweet potato pigment was investigated.Results showed that purple sweet potato pigment displayed different colors and different UV-Vis absorption spectra at different pH values.Both of them changed remarkably and showed a similar trend.When the pH of purple sweet potato pigment solution increased from 2.0 to 8.0, the color of the pigment solution gradually changed from red to purple, then to blue, and the characteristic absorption peak of 237nm and 530nm moved to the longer wavelength respectively.