Abstract: Abscisic acid plays a major role in plant growth and development, and in adaptation to environmental stress. The research of abscisic acid signal transduction is remarkable and advancing rapidly in recent years. This article is a review on mutants nonsensitive and hypersensitive to ABA, ABA binding site and receptor, second messenger (Ca2+, phosphatidylinositol, cADPR, anion channels and H+), reversible protein phosphorylation, and cis-acting elements and trans-acting factors essential for ABA_induced gene expression.