A simulation model was developed to study production system of East Friesian dairy ewes in Mediterranean ecosystem. It includes the simulation of the effects of management changes on production and reproduction of ewes during mating, gestation and lactation. The equations used by the model includes the interactions of physiological condition of the animals, pasture quality, nutritional value of the supplement, stocking rate and feed intake. The model estimates energy partition of maintenance, gestation, weight gain and milk production. Results obtained from the model were compared to those obtained experimentally. Validation of the model shows good adjustment with real production data of East Friesian dairy ewes.