For planning the grazing of rangeland according to difference in body weight and different energy requirements should determine forage requirement of animal unit. In the other hand, daily need of animal in rangeland depends on the quantity and quality of intake forage composition. For this purpose selected part of the rangeland of Fereidunshahr in Isfahan province was classified to vegetation types. In each type of all plant species about 500 grams at flowering stage were collected. Nitrogen (N) and acid detergent fiber (ADF) were measured through chemical analysis. Crude protein, ADF, dry matter digestibility and metabolizable energy either 3 replicates were assessed in the laboratory as indicators of forage quality. The Lori sheep race is user dominant Animal unit. In order to determine the animal unit body weight, from 3 existing herds within 11 unit management with dominant Animal from this race, 10 three and 10 four Dry adult ewes(main structure of the herd), 5 three and 5 four years old rams and 6 month old lambs randomly selected and were weighed in two period. Weighing operation performance once before grazing beginning (first may) and once after the end of grazing season (first September). In conclusion 45 kg body weight as animal unit was calculated and livestock rations of animal requirement in maintenance condition and grazing in rangeland (0.7 times of keeping in a stable) calculated using the MAFF equation. The result showed that animal requirement based on forage quality at flowering stage was 1.09 kg that for grazing session (30% reduction of forage quality) is 1/58 kg in day. Because there are difference in structure of vegetation types and metabolism energy so a permanent quantity of dry forage cannot specify as basic of computation the daily need