In order to realize a high flattening C+L-band fiber source by C band matching L band closely, a superfluorescent light source structure with three-stage two-pumping is presented.Firstly, the experimental equipment is composed of three erbium-doped fibers, two 980 nm LDs,a Wavelength Division Multiplexer (WDM),an isolater(ISO)and a 3 dB coupler.Then, a high flattening C+L-band fiber source is achieved by optimizing the lengths of three erbium-doped fibers and adjusting the powers of two pumps, and the mechanism of production is also analyzed.Experimental results indicate that when the lengths of three fibers are 11.5 m, 53 m, 6.5 m and the powers of the two pumps are 65 mW, 115 mW respectively, the light source can offer a linewidth in 75.68 nm with a power ripple of 3 dB, and the flatness of the spectra from 1 543 nm to 1 603 nm is less than ±1.3 dB without any external spectral filters.The high flattening C+L-band superfluorescent light source can satisfy the requirements of the optical fiber sensing and optical fiber communication systems.