Abstract: Four Xuhuai white goats fitted with permanently ruminal cannulae,proximal duodenal and terminal ileal T-shape cannulaes were used in a 4×4 latin square design to determine the effects of four different ratios of neutral detergent fiber to N-free extract(NDF/NFC)(NDF/NFC were 2.75(A),1.71(B), 1.12(C) and 0.74(D) respectively) in diets on the absorbable amino acids(AAA) of the goats.The study used DAPA and PC respectively as internal marker of rumen bacteria and protozoa to measure the flux and composition of all the AA of bacteria and protozoa to the duodenum.The results showed that:（1）Of the AAA in the small intestine,the flow of bacterial AA in group B was 1.54g/d,which was much higher than group A(0.45 g/d),C(0.36 g/d)and D(0.39 g/d)(P<0.01).The proportion of bacterial AA in group B to the total AAA was 38.4%,which was higher than group D(24.84%)(P<0.05),and significantly higher than group A(13.25%) and C(14.81%)(P<0.01);（2）The flow of protozoal AA in group A was 1.22 g/d,significantly higher than in group B(0.63 g/d),C(0.57 g/d) and D(0.42 g/d)(P<0.01),furthermore, the proportion of that in group A to the total AAA was 36.74%,while group B,C and D was 15.71%,23.45% and 26.75% respectively;（3）Of the AAA from bypass protein,the flow of group A,B was 1.65 g/d,1.84 g/d, both of them were higher than C(1.51 g/d)(P<0.05),and significantly higher than D(0.76 g/d)(P<0.01).The highest proportion to the total AAA was observed in group C(61.37%),which was higher than A(49.13%),D(48.41%)(P<0.05),and significantly higher than B(45.88%)(P<0.01),i.e.the efficiency of dietary AA in the rumen transforming into microbial protein in group B was the greast;（4）Among the AA composition of microbial protein,the AA of protozoa was relatively stable,while the production and composition of Solid Associated Bacteria(SAB) was more stable than that of Liquid Associated Bacteria(LAB).The composition and quantity of the bacterial AAA in the small intestine were directly affected by the change of LAB.