To clarify the gene expression patterns of Eucommia ulmoides Oliver leaves in the process of development at the transcription level,this study compared and analyzed the gene expression level of ‘Huazhong 6’ leaves in different development periods from expanding (April) to falling (October) by digital gene expression profile technology.A total of 3 002 different expression genes were obtained,in which 1 764 up-regulated expression and 1 238 down-regulated expression.These mainly function referred to catalytic activity or oxidoreductase activity,and involved in metabolic process and biological process.Through further pathway enrichment analysis,we found that several related genes of phenylpropanoid biosynthesis pathway were enriched,in which six significantly different expression genes were related to chlorogenic acid synthesis.The gene expression patterns showed that these genes are highly expressed in mid-April and mid-Septemeber,which suggested that these two periods play an important role for chlorogenic acid synthesis.By real-time fluorescent quantitative PCR,6 chlorogenic acid synthesis genes and 12 randomly different expression genes were detected,and the results verified the reliability of digital gene expression profile.This study lays a solid foundation for revealing the molecular regulation mechanism of E.ulmoides Oliver leaves in different development periods,and provides the reference for further clarifying the synthesis mechanism of E.ulmoides Oliver chlorogenic acid and then improve E.ulmoides Oliver chlorogenic acid content by means of molecular breeding.