Extracts from blue petals of Clitoria ternatea have been locally used as a food colorant and cosmetic substance. Anthocyanins extracted from blue C. ternatea petals were characterized using sequential extractions detected by a UV-spectrophotometer and a PDA (photodiode array detector)-HPLC. The patterns of aclyated anthocyanins and phenolic compounds of C. ternatea extracts were compared to known compounds from red grape and red radish extracts. Apart from anthocyanins, C. ternatea petals contained a lot of flavonoid compounds such as p-coumaric acid and ferulic acid. Monomeric anthocyanins of C. ternatea showed unusual appearance with being high stable in buffer pH 4.5. The anthocyanin spectrum performed m a rare pattern of 2 different optimum wavelengths (at 574 and 618 nm), which were disappeared after deacylation. This suggests that acylation at the B ring of the anthocyanins is a critical step in stability of C. ternatea anthocyanins. Moreover the results from alkaline-hydrolysis and acid-hydrolysis reactions revealed that anthocyanins of blue C. ternatea petals were only derived from an anthocyanidin form which is delphinidin.