This study was carried out lo determine the effects of NaHC03 and MgO as buffers on some metabolic incidents under invitro rumen environment. It was determined that the effects of different ratios of sodium bicarbonate (0, 0.5. 1.0, 1.5%) and magnesium oxide {0, 0.25, 0.5, 1.0%) on pH, total volatile fatty acids (TVFA), ammonia nitrogen (NHg-N), buffer capacity (BC), gas production (GP) under the invitro rumen environment that added barley, wheat, corn and oat. The effects of buffers on metabolic energy (ME) of this feeds and digestibility organic matter (DOM) values were also examined. It was found that the differences between pH. BC. GP, ME and DOM values of barley, wheat, corn and oat were significant (P<0.05) but the difference between TVFA and NH3-N values were not significant (P>0.05). In this study NaHC03and MgO supplementation affected differently on the pH. TVFA, NH3-N. BC and GP. While MgO supplementation increased the values of pH, BC and GP. NaHC03 supplementation increased the values of NH3-N significantly (P<0.05). The both of the buffers did not have significant (P>0.05) effects on the values of TVFA. Using the buffers in different ratios changes the values of pH and GP significantly (P<0.05), but they didn't affect the values of TVFA, NH3-N and BC. The incubation time affected the values of examined criterias significantly.