Abstract: To explore effects of root and leaf application of gibberellin（GA₃）on agronomic traits and water use efficiency of rice seedlings, rice seedling cultivation experiments were carried out using rice Jingzhan 1 as experimental material．At 14 and 21 days of seed germination, rice roots and leaves were treated with 0.7, 1.4 and 2.8 mg/L GA₃, respectively, and a control group was set．Agronomic traits such as leaf width and stem diameter, photosynthetic characteristics, and water use efficiency of rice seedlings were detected after rice seeds germinated for 28 days．Results showed that agronomic traits of rice seedlings applied 2.8 mg/L GA₃ to roots had the highest comprehensive value（0.39）, while foliar spraying 0.7 mg/L GA₃ had the highest comprehensive value（0.92）．It was also found that root application of 0.7 mg/L GA₃ improved water use efficiency of rice seedlings by 22.60% compared with control group．Leaf application of 1.4 mg/L GA₃ increased water use efficiency of rice seedlings by 26.39% compared with control group．Effects of root and leaf application of GA₃ on agronomic traits and water use efficiency of rice seedlings were carried out to provide scientific basis and theoretical guidance for sustainable development of high-water-efficiency agriculture in China．