Two rice genotypes with different drought tolerance,namely Jin 23B(drought tolerant)and Zhenshan 97B(drought sensitive),were used to study the antioxidant enzyme activities,soluble sugar and starch contents in spikelets,pistil water potential and pollen number on a stigma under water-deficit stress at the flowering stage,which were involved in the spikelet sterility.Compared with respective controls,drought stress induced more serious decreases of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities and more significant increase of malonaldehyde(MDA)content in spikekets of Zhenshan 97B than in Jin 23B on 9 and 12 days after water stress(DAWS).The soluble sugar and starch contents increased significantly in spikelets of Jin 23B,but decreased significantly in spikelets of Zhenshan 97B during 9-12 DAWS.The pistil maintained higher water potential in Jin 23B than in Zhenshan 97B during 3-6 DAWS and 9-12 DAWS.In addition,water stress induced more significant decrease in the pollen number on a stigma as well as the percentage of unfilled grains in Zhenshan 97B than in Jin 23B.Thus,it is suggested that water stress induced spikelet sterility by damaging antioxidant enzyme activities,reducing carbohydrate content in spikelets and decreasing pistil water potential at the flowering stage in rice. Two rice genotypes with different drought tolerance, namely Jin 23B (drought tolerant) and Zhenshan 97B (drought sensitive), were used to study the antioxidant enzyme activities, soluble sugar and starch contents in spikelets, pistil water potential and pollen number on a stigma under water-deficit stress at the flowering stage, which were involved in the spikelet sterility .Compared with respective controls, drought stress induced more serious decreases in superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities and more significant increase of malonaldehyde (MDA) content in spikelets of Zhenshan 97B than in Jin23B on 9 and 12 days after water stress (DAWS). soluble starch and starch contents increased significantly in spikelets of Jin 23B, but decreased significantly in spikelets of Zhenshan 97B during 9 -12 DAWS. The pistil maintained higher water potential in Jin 23B than in Zhenshan 97B during 3-6 DAWS and 9-12 DAWS. Addition, water stress induced more significant decrease in the it is suggested that water stress induced spikelet sterility by damaging antioxidant enzyme activities, reducing carbohydrate content in spikelets and decreasing pistil water potential at the flowering stage in rice.