The changes in proteome of normal flower and floral reversion buds in longan (Dimocarpus longan Lour.) were studied by using Proteomics method. The results showed that ANS (anthocyanidin synthase) protein was found down-regulated expression in floral reversion buds. ANS cDNA was obtained (GenBank access number: FJ479616) by using RACE method, its full length was 1477 bp, with a 1071 bp open read frame. ANS gene was expressed in E. coli, and a 46 kD heterologous protein was obtained. It suggested that ANS protein play a role in floral reversion in longan.