Abstract: This article reviews the biosynthesis of bioactive GAs in higher plants, the cloning of genes encoding GA biosynthetic enzymes in Arabidopsis, and the successful expression of GA3 gene CYP701A3 in yeast　（Saccharomyces cerevisiae）. The feedback inhibition of GA biosysthesis by active GAs and the signal transduction and reception in feedback regulation are described. GA20_oxidation and/or 3β_hydroxylation are the main steps controled by photoperiod in GA biosynthesis in higher plants.