Abstract: By using restriction enzyme isoschizomers that differ in their sensitivity to methylation of their recognition sites, AFLP analysis is carried out to analyse differences of the methylation state of anonymous CCGG sequences between cold-treated(5℃ for 2 d) and control 9311(Oryza sativa L.) leaves DNA.Demethylation or De novo methylation induced by cold stress are found in some CCGG sites. Some differentially-methylated encoding sequences are isolated, of which a fragment named CIDM7 (cold-inducing differential methylation) is sequenced and executed BLAST against Nipponbare cDNA data, thus we obtain its full length cDNA of 1422 bp encoding a hypothetical F-box protein(425 aa).CIDM7 is demethylated induced by cold stress. Northern blot analysis confirms that CIDM7 gene expression is up-regulated by cold stress. CIDM7 is single copy and lacated on the Nipponbare chromosome 10 (12.56 Mb~12.57 Mb).