Water stress is one of the important ecological factors affecting rice yield and quality, and plants adapt to drought stress using different strategies at different growth stages. A great deal of studies showed that rice plant is very sensitive to water stress during the heading stage. Understanding of the physiological mechanisms of drought resistance for rice is of importance to guide rice water-saving technology. Osmolyte accumulation (OA) is frequently viewed as a key putative mechanism responsible for crop′s tolerance to drought conditions. It is believed that this process has effects on sustaining cell and tissue activity of the plant under drought conditions. When drought occurs, osmotic potential in plant will decrease, organic substances (soluble sugar, proline, amino acid etc.) and inorganic ions (Ca2+、K+、Na+ etc.) will accumulate to some extent. So far, osmotic adjustment of rice plant during water stress has not been widely studied. Rice variety Feng-Hua-Zhan was selected through pot experiment to study the effects of water stress on dry matter accumulation, yield, inorganic and organic osmolytes in leaf and root. Water was withheld for different number of day during heading stage. The results showed that leaf water potential decreased significantly after water stress. Except for soluble sugar in root and leaf which decreased after 12 d of water withheld, organic osmolytes including soluble sugar, proline and free amino acid in leaf and root increased significantly in various drought treatments. The organic osmotic regulated matter increased with increasing severity of water stress. Osmotic adjustment in root was positively correlated to that in leaf, but root was more sensitive to water stress than the leaf did. Organic osmolytes content in root and leaf could return to the normal level after re-watering for short term drought treatment (water being withheld for 3 and 6 d) but not for long term drought treatment (water being withheld for 9 and 12d).Inorganic osmolytes including K+、Ca2+、Mg2+ showed no significant change after drought treatment except for long term drought treatment (water being withheld for 12d). Dry matter accumulation of root, stem，leaf and panicle were also significantly reduced under drought conditions, yield decreased by 12.09%, 4855% and 58.30%, respectively under drought treatment for 6, 9 and 12 d. Drought treatment with different time duration could significantly increase water use efficiency （WUE）of rice leaves, the longer water stress continued, the higher WUE was. These results suggest that rice plant could effectively maintain its physiological equilibrium by adjusting itself to short term drought conditions and the organic osmotic regulated matter responds to droughts more sensitively than the inorganic ions do at heading stage.