From November 2005 to January 2006 when air is clear, a FieldSpec(r) Pro spectroradiometer is used in conjunction with a custom-designed telescope based on integrating sphere to make spectrally continuous measurements of directly transmitted solar spectral irradiance in Hefei. With Langley method, the data is anlyzed to get aerosol optical depth from 350nm to 2500nm. The average optical depth is 0.39156 at 550nm,aerosol optical depth decreases with wavelength increasing. The average Angstrom exponent κ(=0.18895) and ν(=3.26504) are obtained by fitting the optical depth on Junge distribute. The result shows that the small particles are primary in Hefei.