A Spectrophotometric method for the determination of Flavone in the extract of ginkgo biloba leaves (FEGb) was established. In the solution of NaNO_2 and pH 13.20~13.60, FEGb reacts with Al(NO_3)_3 to form a stable and sensitive pink complex, its maximum absorption wavelength is λ_(max)=510 nm. The absorbance (A) was linear with the concentration of FEGb in the range of 4.606~55.27 μg/mL, the method could be opplied to indirect determination of FEGb.