The effect of GA_3 on 28 japonica dwarf varieties was studied.The results showed that the response of the plants to GA_3 of most tested varieties were similar at seedling and shooting stages while there was a little difference in some varieties.In japonica rice,the varieties with sd-1 dwarf gene were sensitive to GA_3.However,not all the GA_3-sensitive varieties have sd-1 gene.It is concluded that Ai-4 and Ziyeai might carry non-allelic to sd-1.The effect of GA_3 on the elements of plant height was different.Of all elements of plant height,the response of first and second base internodes to GA_3 were most significant.