Effects of ugareet pulp substitution for total mixed ration (TMR), which was included of alfalfa hay, barley grain and corn grain, on feed intake, growth performance, chewing behavior, ruminal fermentation, blood parameters and digestibility were evaluated by using twenty-six Lori(Iranian sheep breed) male lambs in a Completely randomized design. Sheep with an average body weight 28.2 ± 3.6 kg and age of 5 to 6 months were divided into four groups, fed four types of rations. 1 st ration was without sugar beet pulp. 2 nd ration included 10% sugar beet pulp and the 3 rd and 4 th rations were included 20% and 30% sugar beet pulp, respectively. All rations were offered ad lib and feeding experiment lasted 84 days (three periods that each period was 28 days). The results showed increasing sugar beet pulp in diets caused to decrease in DMI and daily feed intake as % of body weight. Digestibility of DM, OM and CP was similar in four groups but digestibility of NDF increased by addition of sugar beet pulp in diets. Incorporation of sugar beet pulp in sheep rations had no significantly effect on final body weight, growth to feed ratio, cost to gain ratio, hot carcass weight, dressing percentage and all offal’s as % of fasted body weight. ADG tended to decrease linearly ( P=0.09 ) by addition sugar beet pulp in diets. Rumen pH and TVFA's were not affected by experimental diets. Inclusion sugar beet pulp in diets caused to increase in acetate concentration and acetate to propionate ratio, and decrease in propionate concentration. Incorporation of sugar beet pulp in sheep rations had no significantly effect on urine pH and all parameters of blood plasma. Geometric mean particle size and peNDF ?8mm contents was similar in four rations. peNDF ?1.18mm contents increased by increasing sugar beet pulp in diets. Incorporation of sugar beet pulp in diets has no significant effect on rumination time per Kg peNDF ?8mm intake , but caused to decrease in rumination time per day, per Kg DM, per Kg NDF, and per Kg peNDF ?1.18mm intake. Total chewing time per day and per kg NDF intake tended to decrease linearly ( P=0.07 ) by addition sugar beet pulp in diets. Total chewing time per kg DM, peNDF ?8mm intake was similar in four groups. Total chewing time per kg peNDF ?1.18mm intake decreased linearly by addition sugar beet pulp in diets. The present study indicated that inclusion of sugar beet pulp in diets for fattening lambs up to 20% is safe and economically feasible. Keywords : sugar beet pulp, lamb, growth performance, digestion coefficients, chewing behavior, ruminal fermentation.