This experiment was carried out to investigate the effects of urea treatment, amount and source of energy and protein supplementation on the intake, fiber fractions digestibility of rice or soybean straw based diets with sheep. Two supplemental energy sources (maize or molasses + maize) and three sources of protein (fish meal, soybean meal and urea) were used. Sixteen metabolism trials were conducted to evaluate the nutritive values of the following rations: Untreated rice straw (URS) + Maize (M) + Fish meal (FM) + Urea (U). URS+ M + Soybean meal (SBM) + FM + U URS + Molasses (MO) + M + FM + U URS+ MO + M + SBM + U Treated rice straw  (TRS) + M + FM. TRS+ MO + FM. TRS+ MO+ M + fish meal FM. TRS+ MO+ M + SBM Untretaed soybean straw (USBS) + M + FM + U USBS + M+ SBM + FM + U USBS + MO + M + FM + U USBS + MO+ M + SBM+ U Treated soybean straw (TSBS) + M + FM. TSBS + MO + FM. TSBS + MO+ M + FM. TSBS + MO+ M + SBM The experimental rations were formulated to contain about 80 g/kg DMI or higher in CP content when ruminants are given roughage ad lib. in order to maximizing  the rumen microbial growth and activity (Van Soest, 1982). The results showed that, there were pronounced effect of urea treatment on the chemical composition of RS and SBS. The digestibility of DM, OM, CF, NDF, ADF, hemicelluloise, cellulose and ADL of TRS rations were higher (P<0.01) than URS rations. The digestibility of CF was higher (P<0.05) when adding FM (76.9) than adding SBM (75.0%) in TRS rations. Also, digestibility of CF, NDF and hemicellulose were higher (P<0.05) when feeding on molasses and maize than feeding on maize in TRS roughage. The effect of urea treatment on dry matter intake (DMI) and TDN value were higher (P<0.01) than untreated materials. The TDN value (%) of ration containing TRS with FM and maize was (59.87%) higher than the other RS rations. The TDN value (%) of TSBS with SBM and maize plus molasses was (54.01%)higher than the other SBS rations. The results showed that there were significant differences as the effect of the type of the roughage. The urea treatment with adding protein and carbohydrate source improved RS digestion more than SBS.