In order to reveal the influence mechanism of fulvic acid on the photosynthesis and antioxidant enzyme activity of Avena sativa under drought stress, this study selected A. sativa variety ‘Yanke 2’ as the material, adopted pot experiment, took normal water supply (75% of field capacity) as the control (CK), set drought stress treatment (45% of field capacity, D0), D0 and spraying fulvic acid of different concentrations (0, 200, 400, 600, 800, 1 000 mg/L) treatment (D1-D5), The dry and fresh weight, photosynthetic performance and antioxidant enzyme activity of A. sativa were measured. The results showed that: (1) compared with CK, under drought stress, the aboveground fresh and dry weight, leaf photosynthetic pigment content, net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s) of A. sativa seedlings were significantly reduced, and F_v/F_m, qP, ETR and Φ_PSⅡdecreased significantly. The activities of SOD, POD and CAT in leaves were increased by 25.68%, 19.98% and 7.29% respectively. (2) Compared with D0, after spraying 600 mg/L fulvic acid, the shoot fresh weight and dry weight of A. sativa seedlings were significantly increased by 28.59% and 39.13%, respectively. Chlorophyll a, chlorophyll a+b, carotenoids content and P_n, G_s, T_r, F_v/F_m, Φ_PSⅡ and ETR increased by 25.17%, 21.03%, 47.37% and 74.38%, 26.47%, 43.34% and 6.49%, 69.57% and 70.71%, respectively, and C_i, F_o and NPQ decreased by 19.52%, 13.32% and 43.75%, respectively. (3) Under drought stress, the activities of SOD, POD and CAT in leaves of seedlings sprayed with fulvic acid of different concentrations were significantly increased compared with D0 treatment. Among them, the activities of SOD, POD and CAT in leaves sprayed with fulvic acid of 600 mg/L were the highest, which were significantly increased by 12.19%, 76.57% and 55.26% compared with D0 treatment. The study shows that foliar spraying suitable concentration of fulvic acid can improve the photosynthesis and antioxidant capacity of A. sativa seedlings under drought stress, alleviate the damage of drought to A. sativa seedlings, and then promote the growth of A. sativa seedlings, and the effect of foliar spraying of 600 mg/L fulvic acid is the best.