We used an efficient system to create rice mutant by Ac/Ds transposon insertion mutagenesis, such as selected homozygous mutant in dwarf phenotypes. We reported here the identification of function of dwarf OsGASD gene(Oryza sativa Gibberellin Acid Sensitive Dwarf). OsGASD gene encodes a 344 amino acid polypeptide and no homology proteins in Gene Bank. The osgasd mutnat was sensitive to exogenous gibberellic acid(GA) level. We performed experiment to controlled expression the OsGASD gene, its role in plant development, a quantitative analysis of endogenous GA content and sensitivity to GA. The osgasd mutant includes smaller amount of active GAs than wild-type. osgasd mutant plant of GA biosynthesis pathway causes GA deficiency and dwarf plants, and endogenous GA suppliance can restore the wild type phenotype in this mutant. There result indicated that OsGASD gene regulated the elongation of shoot, stem and plant height. The increased expression of OsGASD gene dramatically induces expression of the factors associated with GA biosynthesis, whereas osgasd mutant suppression of the factors associated with GA biosynthesis, loading to dwarf phenotypes. That applied GA3 at the plant development stage to survey the response of OsGASD gene to GA3. We suggest that OsGASD gene is related to factors of GA biosynthesis pathway regulating rice internodes development.