This study aimed to investigate the effects of nano-titanium dioxide(nTiO₂) priming on seed germination and seedling growth of barley under drought stress, and to determine the optimal combination of priming time and concentration. Using a barley cultivar Ganpi 8 as material, drought stress was simulated with 22% polyethylene glycol-6000. Three priming times(12, 24, and 36 h) and five nTiO₂ concentrations(0, 250, 500, 750, and 1 000 mg·L^-1) were set, and the diifferences in 13 indices including germination rate, germination potential, germination index, vigor index, root length, shoot length, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, root-shoot ratio, root number, and coleoptile length among different treatments were compared and analyzed. Two-way ANOVA showed that priming time, concentration, and their interaction had significant effects on most indices(P<0.05 or P<0.01), with significant interaction effects between time and concentration. Compared with the unprimed control(CK), hydro-priming(HP) significantly improved some germination and growth indices. Under 12 h priming time, 750 mg·L^-1 nTiO₂ treatment showed the best effect, with germination rate, germination potential, germination index, and vigor index significantly increased by 8.0 percentage points, 44.7 percentage points, 69.4%, and 145.8%, respectively, compared with hydro-priming, and root length and shoot length increased by 72.5% and 5.2%, respectively. Under 24 h priming time, 500 mg·L^-1 nTiO₂ treatment performed best, with the above germination indices significantly increased by 18.7 percentage points, 10.7 percentage points, 28.9%, and 102.9%, respectively, and root fresh weight and root length increased by 40.5% and 7.0%, respectively. When priming time was extended to 36 h or concentration increased to 1 000 mg·L^-1, nTiO₂ showed inhibitory effects, with germination rate and root growth indices significantly lower than those of hydro-priming. This indicates that appropriate time and concentration of nTiO₂ priming can effectively promote barley seed germination and seedling growth under drought stress, where 12 h priming with 750 mg·L^-1 nTiO₂ and 24 h priming with 500 mg·L^-1 nTiO₂ showed better effects under the experimental conditions, especially the comprehensive effect of 24 h priming with 500 mg·L^-1 nTiO₂ showing the best overall performance.