Abstract: This experiment was conducted to investigate the effects of different dietary NFC/NDF ratios on ruminal microorganisms and pH in dairy goats under the condition of subacute ruminal acidosis（SARA）.In this self-contrast experiment Guanzhong lactating dairy goats fitted with permanent rumen cannula were selected.The experiment was composed of 4 periods with 10 d in each period.The goats were fed diets with different NFC/NDF ratios,which were 1.02（period Ⅰ）,1.24（period Ⅱ）,1.63（period Ⅲ） and 2.58（period Ⅳ）,respectively.Meanwhile,subacute rumen acidosis（SARA） was induced by gradually increasing the content of concentrate.The results showed as follows： the ruminal pH decreased significantly with the increasing of dietary NFC/NDF rations（P0.05）,and the decreasing scale increased;the number of amylolytic bacteria increased significantly with the gradually increasing dietary NFC/NDF ratios（P0.01）,the number of ruminal total bacterial,Lactobaillus and Fusobacterium necrophorum increased significantly when the ratio was 1.63（P0.05）,and the number of Megasphera elsdenii and Selenomonas ruminantium increased significantly when the ratio was 2.58（P0.05）;the number of total ciliates was the lowest in period Ⅳ,but the populations of Strepococcus bovis did not change obviously（P0.05）.The results indicated that when the NFC/NDF ratio was 1.63,the majority of rumen bacteria which related to the degradation of carbohydrates increased obviously,especially during SARA period,but the population of total ciliates decreased to the lowest level.