Abstract: A forward and a reverse suppression subtractive cDNA library were constructed，using cDNAs from the TDZ-treated and non-treated axillary buds of Dendrobium nobile Lindl. A total of 314 and 59 recombinant clones were identified from the forward and reverse SSH library respectively，by PCR and reverse Northern blotting. All of these clones were sequenced and assembled，finally 39 ESTs from the forward library and 21 ESTs from the reverse library were obtained. Effects of TDZ on the transcription of some ESTs were confirmed by semi RT-PCR. Of these sequences，twenty genes were not homologious to the reported genes in GenBank，the rest were classified into photosynthesis，biosynthesis，metabolism or regulatory function. A sequence homologious to MADS-box genes and a homology of Sos were identified from the reverse library，and several retrotransposons were characterized from the forward library，these results indicated that TDZ could promote the flowering of D. nobile，by affecting the transcriptions of some transcription factors and signal genes.

Key words: Dendrobium nobile Lindl., flowering；cytokinin, suppression subtractive hybridization（SSH）, retrotransposon