Two experiments were conducted to evaluate the effect of resveratrol on methanogenesis and microbial flora in Dorper × thin-tailed Han crossbred ewes. In experiment 1, Eighteen ewes (60.0 ± 1.73 kg BW) were assigned to 2 dietary treatments, a basal diet and a basal diet supplemented with resveratrol (0.25 g/head·d), to investigate the effect of resveratrol on nutrient digestibility and nitrogen balance. In experiment 2, 6 ewes (64.0 ± 1.85 kg BW) with ruminal cannulas were assigned to the identical dietary treatments used in experiment 1 according to change over design, to investigate supplementary resveratrol on ruminal fermentation and microbial flora using q-PCR. The digestibility and nitrogen balance data were analyzed using t-test procedures in SAS. Data referring to ruminal fermentation parameters (ruminal pH, ammonia, and volatile fatty acid) and microbial flora measured at each sampling time were analyzed using a repeated measures one-way ANOVA. Significant differences were accepted when P < 0.05. The results showed that supplementary resveratrol improved the digestibility of organic matter (P < 0.001), nitrogen (P = 0.007), neutral detergent fiber (P < 0.001), and acid detergent fiber (P < 0.001). The excretion of fecal N was reduced (P = 0.007), whereas that of urinary N increased (P = 0.002), which led to an unchanged N retention (P = 0.157). Both CO₂ and CH₄ output scaled to digestible dry matter intake decreased from 602.5 to 518.7 (P = 0.039) and 68.2 to 56.6 (P < 0.001), respectively. Ruminal pH (P = 0.341), ammonia (P = 0.512), and total volatile fatty acid (P = 0.249) were unaffected by resveratrol. The molar proportion of propionate increased from 13.1 to 17.5% (P < 0.001) while that of butyrate decreased from 11.0 to 9.55% (P < 0.001). The ratio of acetate to propionate decreased from 5.44 to 3.96 (P < 0.001). Supplementary resveratrol increased ruminal population of F. succinogenes, R. albus, and B. fibrisolvens (P < 0.001) while decreased protozoa and methanogens (P < 0.001). In conclusion, dietary resveratrol inhibited methanogenesis without adversely affecting ruminal fermentation.