【Abstract】 Objective Carrying out the preliminary research on the value of Biotechnology Fulvic Acid (BFA) as nutritional additives in functional feed, based on the biochemistry and intestinal flora index of mammals(SD rats) affected by BFA. Methods Feed four group of mammals (SD rats) with normal feedingstuff mixed of four kind of BFA(lactobacillus fermented BFA, bacillus fermented BFA, yeast fermented BFA and Mixed fermentation BFA) with the proportion of 1.5%, compare with the group of mammals (SD rats) feeding without BFA, observe the indicator of nutrition and health condition, including weight gain, feed weight ratio, routine blood test, blood biochemical indices and quantitative analysis of intestinal flora. Results 1. Routine blood test: WBC, MON, NEU decreased, the difference is significant(P<0.05,P<0.01);NEU of bacillus fermented BFA group decreased，the difference is significant(P<0.05). 2.Blood biochemical indices: TP, Alb, A/G of lactobacillus fermented BFA group increased, the difference is significant(P<0.05,P<0.01,P<0.05),TBIL decreased, the difference is significant(P<0.05);TBIL of bacillus fermented BFA group decreased, the difference is significant(P<0.01). 3.weight gain: the Total Weight Gain and the Daily Weight Gain of Mixed fermentation BFA group is evidently higher (P<0.05);Weight ratio of lactobacillus fermented BFA group, bacillus fermented BFA group, yeast fermented BFA group, Mixed fermentation BFA group to the normal group is 6.70,6.74,6.49,6.09,6.77. 4.Quantitative analysis of intestinal flora: The number of Escherichia coli of lactobacillus fermented BFA group and Mixed fermentation BFA group decreased，the difference is significant(P<0.05),meanwhile the number of bacillus acidi lactici evidently increased(P<0.05). Conclusion BFA improves the nutriture and health indicator of SD rats. the nutritional effects of Mixed fermentation BFA is the best of all. The experiment proved the mixed fermentation BFA is remarkably valuable for improving health condition of mammals as nutritional additives in functional feed.