Several dwarf plants occurred in potato lines transformed with StERF3 over expression vector and the influencing factors of the dwarfism was investigated.Gene expression test revealed that StERF3 expression level in dwarf plants was lower than that of control.StERF3 gene expression decreased in the interference transgenic lines,but no dwarf plants appeared.The results indicated that the dwarfism was not related with the expression of StERF3 gene.Medium supplemented with 0.5 mg/mL exogenous GA3 could improve the growth of dwarf plants in vitro to some extent.Most of the dwarf lines contained 3-4 copies.Multi-copy integration always led to transgenic silencing.In conclusion,the dwarf might be caused by multiple copies integration into the genomic DNA which interrupted the genes associated with GA3 pathway.