Abstract: The aim is to elucidate the spatiotemporal expression of Cycloartenol synthase (CAS), Dammarenediol-Ⅱ-synthase (DS) and β-amyrine synthase (β- AS) gene and their relationship and the total saponin content of Panax japonicus var. major Leaves, stems, flowers and rhizomes of Panax japonicus var. major were used as materials, and the expressions ofCAS ,DS and β-AS in different phases were determined by real-time RT-PCR, and the relationship between gene expression and total saponin content was analyzed. CAS ,DS and β-AS were highly expressed in the overground part of Panax japonicus var. major, and were low expressed in rhizomes. The expression levels of CAS showed a tendency of high- low- high from May to September, butDS and β-AS showed the reverse trend. The change of total saponin content showed an“S” curve and it was positively correlated with the expression ofDS and β-AS at the early stage of Panax japonicus var. major. It is speculated that leaf may be the initial and primary site of saponins synthesis and rhizome may be the site of partial saponins synthesis at the later growth stage of Panax japonicus var. major.