Flavonoids are the pharmacologically important chemical groups. NaNO₂-Al(NO₃)₃-NaOH colorimetry assay for determination of total flavonoids in health foods have some defects. In this work, contribution of six key flavonoids components of extract of Ginkgo biloba leaves to total flavonoids content in the NaNO₂-Al(NO₃)₃-NaOH colorimetry assay were evaluated. Results showed that quercitin made the most contribution to total flavonoids content. Sample quantity, alcohol concentration of eluant, and ultrasonic times in this assay were evaluated. Alcohol concentration of eluant and ultrasonic times affected total flavonoids content in HZ Capsules. By using the improved method, total flavonoids content of HZ Capsules were between 1.68 g/100 g and 1.83 g/100 g, the average contents ranged from 1.71 g/100 g to 1.77 g/100 g, the relative standard deviation were between 1.36% and 4.08%, the recoveries of rutin ranged from 94.05% to 100.44%. Results from the repetitive test, precsiion test and recovery test indicated that this improved method could meet the demand for determination of total flavonoids in HZ Capsules to quality control during processing.