Abstract: A normalized full-length cDNA library was constructed with the banana roots，by DSN（duplex-specific nuclease）normalization method combined with SMART（switching mechanism at 5′end of RNA transcript）technique. The titer of unamplified cDNA library was about 1.1 × 106 cfu · mL-1，the capacity was 5 × 106 clones，and the recombination ratio was more than 95%. The average insertion size was above 1 kb which suggested that the quality of the cDNA was better. Random selected 192 clones were sequenced and 179 high quality EST were obtained，which included 5 contings and 174 singlets. The redundancy was 2.35%. With small scale sequencing，145 unigenes were obtained. The analysis result indicated the library was efficient and reliable. Selecting 3 genes which is homological with other plants’ anti-abiotic stress genes from above sequences，they are expressed under drought，low temperature and salt tress using RT-PCR method. The result suggested that the 3 genes had different expression under different stresses.

Key words: banana, roots, normalized, cDNA library, gene, expression