Abstract: For the problem of the nitrogen element in the aminoglycoside molecule in the cell wall of Auricularia auricular, it was not accurate to determine the contents of total dietary fiber of auricularia auricula samples by enzyme-weighted method and enzyme-chemical method by AOAC directly, without considering the non-protein nitrogen. The non-protein nitrogen in the auricularia auricula samples were determined in this paper, and the difference on the determination auricularia auricula dietary fiber was compared between AOAC official method 991. 43 and its correction method. Firstly, the optimum condition to determine the recovery of aminoglycoside in chitin was gained, first stage was 60W and 60s, and second stage was 100W and 120s, upon the condition of 8mol/L and 8mL HCl at microwave digestion method. The result showed that there would be 3. 18% deviation with AOAC official method 991. 43 directly, and the correction to AOAC official method was necessary at the determination of edible fungi dietary fiber with chitin.