Abstract: The objective of this study was to investigate the effects of thyme methanolic extract on ruminal Dry Matter (DM) degradation parameters of sunflower meal. Treatments were: Sunflower meal (no additive), thyme methanolic extract (0.15 ml/30 ml buffered rumen fluid). In situ rumen degradability was performed with of three Gezel rams rumen fistulaed in times at 0, 2, 4, 8, 16, 24 and 48 h. Potential degradation (a+b) for sunflower meal and thyme methanolic extract (0.15 ml/30 ml buffered rumen fluid) were estimated, 76.82 and 80.47%, respectively. Effective rumen degradable dry matter for sunflower meal and thyme methanolic extract (0.15 ml/30 ml buffered rumen fluid) at a rate of 0.08/h, 45.33 and 50.03%, respectively were estimated. Thyme methanolic extract (0.15 ml/30 ml buffered rumen fluid) treatments significantly decreased dry matter gradability of sunflower meal on different incubation times. Although thyme methanolic extract (0.15 ml/30 ml buffered rumen fluid) decreased (p<0.05) the water soluble fraction (a) and Effective Rumen Degradability of Dry Mattre (ERDM) at a rate of 0.02/h but increased (p<0.05) the potentially degradable fraction (b) of DM, constant rate of degradation (c), total degradability (a+b) and Effective Rumen Degradability of Dry Matter (ERDM) at a rate of 0.05 and 0.08/h.