Based on experimental research on three kinds of C+L band Erbium-doped fiber amplified spontaneous emission (ASE) light source including signal-stage, two-stage and three-stage structure, the characteristics are compared and the advantages and disadvantages are analyzed. Results show that C band and L band spectrum of C+L band Erbium-doped fiber ASE light source with single-stage and two-stage structure is difficult to realize optimal matching and flatness is not ideal. Though the three-stage two-pumping structure light source is more complicated than that of the other two structures, the flatness of output spectrum is better through optimizing light source parameters. So the application requirements from distributed fiber Bragg grating (FBG) sensing system, long range fiber communication system, fiber gyroscope and spectrum testing are better satisfied.