The rice height has been proposed to involve gibberellin biosynthesis. In order to regulate rice height, we suppressed expression of OsGA20ox2 by the double-stranded RNA interference (RNAi) method. For this purpose, we constructed two different RNAi vectors, pCH1CK and pCH12CK, then performed Agrobacterium-mediated transformation of rice varieties QX1 and Zhongzuo0201. The RNAi transgenic lines derived from pCH1CK and pCH12CK demonstrated a clear reduction in height compared with the control plants (P < 0.01). The height of dwarf lines from pCH1CK and pCH12CK were about 75–84% and 54–74% of that of the control plants, respectively. Transcripts for semi-dwarf lines from pCH1CK and pCH12CK were also reduced in comparison with the control plants. Analyses of seeds per panicle, 1,000-grain weight, and seed yield per plant suggested that the RNAi semi-dwarf lines showed stable grain yield compared with the wild-type plants. We further showed that the RNAi semi-dwarf lines could be restored to normal plant height by applying exogenous GA3. The results also indicate that different fragment of the same RNAi target can be practically applied to produce different extent semi-dwarf of rice plants.