In this study,Bougainvillea glabra ‘Mrs Butt’ was used to analyze the regulation mechanism of ABA in promoting its flowering promotion.The results showed that:(1)50 mg·L^-1 ABA treatment promotes B.glabra flowering,and 10 μmol·L^-1 NDGA (Nordihydroguaiaretic acid,one kind of ABA biosynthesis inhibitor) treatment inhibited this effect.(2)Exogenous ABA treatment increased the content of endogenous ABA and the enzyme content and activity of nine-cis-epoxy carotenoid dioxygenase (NCED) in B.glabra leaves,and these inductions could be inhibited by NDGA treatment.(3)The full length of cloned NCED gene was 2 380 bp,and the putative encoding protein is 618 aa,which showed the highest homology with FvNCED1 in the strawberry,and was named as BgNCED1.(4)Real-time PCR results showed that the expression of BgNCED1 was significantly induced by ABA treatment,and 10 μmol·L^-1 NDGA could significantly inhibit the induction effect.This expression pattern was similar to the changes of endogenous ABA content and NCED enzyme activity.Therefore,exogenous ABA may enhance endogenous ABA biosynthesis through the induction of BgNCED1 expression,which promoted B.glabra from vegetative growth to reproductive growth,and ultimately make it flowering early.