This study was conducted to examine the nutrient digestibility and ruminal fermentation characteristics in sheep fed dried mugwort and mugwort silage for 5% levels of rice straw in the basal diet, and mugwort pellet for 5% levels of concentrate in the basal diet. For the experiment, they were given a basal diet containing of rice straw and concentrate mixed at a 3: 7 ratio (DM basis). The treatments were designed as a 4 ${ imes}$ 4 Latin square design with four sheep (50.2 kg body weight). The digestibility of crude protein was increased (p < 0.05) to 4.6 - 6.2 % in sheep fed mugwort silage treatments (60.23 %) compared with those of control (54.08 %) and dried mugwort treatment (55.67 %). That of ether extract was iicreased (p < 0.05) to 4.8 - 8.8 % in sheep fed mugwort silage treatments (80.22 %) compared with those of control (71.47 %) and dried mugwort treatment (75.46 %). In the dry matter intake, mugwort silage treatment (904.44 g) was the hightest and mugwort pellet treatment, dried mugwort treatment and control were 810.66 g, 780.66 g and 742.18 g, respectively. The ruminal pH in all treatments were rapidly decreased (p < 0.05) at 0.5 and 1 hour after feeding and slowly increased at 2, 4 and 8 hours after feeding, especially mugwort silage treatment. The ammonia nitrogen concentrations were the highest (p < 0.05) in sheep fed mugwort silage treatment (11.24 - 12.05mg / 100 rnz) at 0.5 and 2 hours after feeding. The ruminal concentrations of acetic acid (6.06 mmol /100 $mell$) and propionic acid (2.35 mmol/ 100 mz) were an increased (p < 0.05) at the mugwort silage treatments at 1 and 2 hours after feeding. Purine derivatives out put (13.41 mmol / d) and microbial protein production (11.61 mmol / d) were increased (p < 0.05) compared with those of control (5.42 and 4.93 mmol / d).