ASE broadband light source based on erbium-doped fiber (EDF), as an excellent broadband light source, has attracted much attention. The output spectral characteristics of ASE broadband light source based on EDF with single- and double-pass configurations are respectively investigated experimentally. With the central pump wavelength of 1480 nm, the influences of EDF length and pump power on output spectral width and flatness are studied for both the single- and double-pass configuration ASE sources. It is found that the power of ASE source located in the L-band, especially in the wavelength range of 1570~1620 nm, for the double-pass configuration may be enhanced, giving a wider and flatter spectrum in whole C- and L-bands by comparing to the output spectra for the single-pass configuration. All the experimental results will be helpful for the developments of ASE broadband light source.