This experiment was conducted to investigate the effects of different dietary NFC/NDF ratios on ruminal microorganisms and pH in dairy goats under subacute ruminal acidosis (SARA). In this self controlled study, six rumen-cannulated Guanzhong lactating dairy goats were selected and self-control method was used. The experiment was carried out for 4 periods with 10 d 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 ruminal acidosis (SARA) was induced by the gradually increasing concentrate. The results showed as follows: the ruminal pH decreased significantly with the increasing of dietary NFC/NDF rations (P<0.05), and the decreasing scale increased; the number of amylolytic bacteria increased remarkably with the gradually increasing dietary NFC/NDF ratios (P<0.01), the number of ruminal total bacterial, Lactobaillus and Fusobacterium necrophorum increased significantly when the ratio was 1.63 (P<0.05), and the number of Megasphera elsdenii and Selenomonas ruminantium increased significantly when the ratio was 2.58 (P<0.05); the number of total ciliates dropped to the lowest in period Ⅳ, but the populations of Strepococcus bovis did not change obviously (P>0.05). The results indicate that when the NFC/NDF ratio is 1.63, the majority of rumen bacteria which related to the decomposition of carbohydrates increases obviously, especially during SARA period, but the population of total ciliates falls to the lowest.［Chinese Journal of Animal Nutrition，2011，23（4）：597 -603］