[Objective] To establish a method for determining the content of total flavonoids in residues, so as to provide basis for the reuse of Sophora alopecuroides L. [Method] The content of total flavonoids in S. alopecuroides residues was determined by NaNO2-Al(NO3)3-NaOH spectrophotometry. [Result] The regression equation was Y=11.403X+0.002 1, R=0.999 8, confirming a good linear relationship between the concentration and absorbance of rutin. The recovery of total flavonoids ranged from 98.67% to 100.33% with the RSD of 1.65% (n=9). In addition, the average content of total flavonoids in S. alopecuroides was determined as 3.90 mg/g. [Conclusion] The method is easy, convenient and low cost, which can be used for determining the content of total flavonoids in S. alopecuroides residues. [Objective] To establish a method for determining the content of total flavonoids in residues, so as to provide basis for the reuse of Sophora alopecuroides L. [Method] The content of total flavonoids in S. alopecuroides residues was determined by NaNO2-Al ( NO3) 3-NaOH spectrophotometry. [Result] The regression equation was Y = 11.403X + 0.002 1, R = 0.999 8, confirming a good linear relationship between the concentration and absorbance of rutin. The recovery of total flavonoids ranged from 98.67% to 100.33% with the RSD of 1.65% (n = 9). In addition, the average content of total flavonoids in S. alopecuroides was determined as 3.90 mg / g. [Conclusion] The method is easy, convenient and low cost, which can be used for determining the content of total flavonoids in S. alopecuroides residues.