Interactions of lignocellulosic components during fiber analysis were investigated using the highly adopted compositional analysis procedure from the National Renewable Energy Laboratory(NREL),USA.Synthetic feedstock samples were used to study the effects of lignin/protein,cellulose/protein,and xylan/protein interaction on carbohydrate analysis.Disregarding structural influence in the synthetic samples,lignin and protein components were the most significant(P<0.05)factors on cellulose analysis.Measured xylan was consistent and unaffected by content variation throughout the synthetic analysis.Validation of the observed relationships from synthetic feedstocks was fulfilled using real lignocellulosic feedstocks:corn stover,poplar,and alfalfa,in which similar results have been obtained,excluding cellulose analysis of poplar under higher protein content and xylan analysis of alfalfa under higher protein content.The results elucidated that according to their protein and lignin contents of different lignocellulosic materials,accuracy of the NREL method on cellulose and xylan analyses could be improved by applying a stronger extraction step to replace water/ethanol extraction. Interactions of lignocellulosic components during fiber analysis were investigated using the highly adopted compositional analysis procedure from the National Renewable Energy Laboratory (NREL), USA. Synthetic feedstock samples were used to study the effects of lignin / protein, cellulose / protein, and xylan / protein interaction on carbohydrate analysis. Disregarding structural influence in the synthetic samples, lignin and protein components were the most significant (P <0.05) factors on cellulose analysis. Measured xylan was consistent and unaffected by content variation throughout the synthetic analysis. Risk of the observed relationships from synthetic feedstocks was fulfilled using real lignocellulosic feedstocks: corn stover, poplar, and alfalfa, in which similar results have been obtained, excluding cellulose analysis of poplar under higher protein content and xylan analysis of alfalfa under higher protein content. The results elucidated that according according to to their protein and lignin contents of di fferent lignocellulosic materials, accuracy of the NREL method on cellulose and xylan analyzes could be improved by applying a stronger extraction step to replace water / ethanol extraction.