The effects of nicotinic acid (NA) on lactate and volatile fatty acid (VFA) concentrations, and related enzyme activities in rumen of Jinjiang cattle were studied in this experiment. Three healthy Jinjiang cattle with permanent rumen cannulas and an average body weight of (275±20) kg were selected. Using rumen acidism method induced by gradually increasing concentrate ratio, the experiment was divided into four test periods: test periods Ⅰ, Ⅱ and Ⅲ were fed diets with the concentrate ratios of 60%, 70% and 80%, respectively; test period Ⅳ was fed the diet with 80% concentrate ratio + 800 mg/kg NA, and every test period lasted for 10 days. The results showed as follows: 1) in test periods Ⅰ, Ⅱ and Ⅲ, under the condition of diets without NA, pH in rumen was significantly decreased with the increase of concentrate ratio (P<0.05); the concentrations of acetate, propionate, butyrate and total VFA were significantly increased with the increase of concentrate ratio (P<0.05), there was significant difference between 60% and 70% or 80% concentrate ratio (P<0.05), but no significant difference was found between 70% and 80% concentrate ratio (P＞0.05). Rumen pyruvate and lactate concentrations, and lactate/pyruvate were increased with the increase of concentrate ratio, no significant difference was found between 70% and 60% concentrate ratio (P＞0.05), but there was significant difference between 80% and 70% or 60% concentrate ratio (P<0.05). There were no significant differences in the concentrations of oxidized nicotinamide adenine dinucleotide (NAD⁺) and reduced nicotinamide adenine dinucleotide NADH, and NADH/NAD⁺ in this three test periods (P＞0.05), but with the increase of concentrate ratio, NAD⁺ concentration was reduced, and NADH concentration and NADH/NAD⁺ were increased. 2) In test periods Ⅲ and Ⅳ, under the condition of 80% concentrate ratio, the supplementation of NA significantly increased rumen pH, propionate and total VFA concentrations (P<0.05), and significantly decreased pyruvate and lactate concentrations, and lactate/pyruvic compared with no NA supplementation (P<0.05), but there were no significant differences in the concentrations of acetate and butyrate, and acetate/propionate (P＞0.05). The supplementation of NA did not significantly affect NAD⁺ and NADH concentrations and lactate dehydrogenase activity compared with no NA supplementation (P＞0.05), but there was a trend to increase NAD⁺ concentration and decrease NADH concentration and lactate dehydrogenase activity (P＞0.05). 3) The lactate dehydrogenase activity in rumen was not detected in test periods Ⅰ, Ⅱ and Ⅳ, and only found in the test period Ⅲ of 80% concentrate ratio (without NA), and the activity was 132.9 U/mL. In conclusion, the supplementation of NA can increase NAD⁺ concentration, decrease NADH concentration and lactate dehydrogenase activity, and inhibit lactate dehydrogenase activity and lactic acid concentration. Therefore, NA may be play a role in alleviate acid shock or acidosis in rumen.