This study was conducted to investigate the effect of sulphur coated urea for substitution of as nitrogen sources of diets. Digestibility, fermentation and blood parameters and microbial protein synthesis were investigated. Four male Raeini goats were used in 4 x 4 Latin square experimental design. Each experimental period was 21d with 16d adaption period and 5d for collecting samples. The experimental diets were: 1) control (soybean meal), 2) containing 1% urea, 3) containing 1.4% of sulphur coated urea, and 4) containing 2.15% of sulphur coated urea. Dry matter (DM), organic matter (OM) and feces nitrogen were highest in control group. Also, digestibility of DM, OM and nitrogen were reduced with feeding diet containing 1% urea. Urinary nitrogen excretion between treatments was significantly different. Ruminal NH3–N, blood glucose and blood urea N in animals fed diet containing 2.15% sulphur coated urea were significantly lower compared with the diet containing 1% urea. Microbial protein synthesis, total purine derivatives excretion (mmol/day), nitrogen content of purine derivatives and allantoin excretion were lowest in animals fed diet containing 1% urea. Purine nitrogen index and microbial nitrogen to total urinary nitrogen ratio were the same in all treatments but those values were reduced when animals fed diet containing 1% urea. In conclusion, using sulphur coated urea had a reduction effect on nitrogen excretion and increased microbial protein synthesis.