The invention relates to an ultra-fluorescence optical fiber light source, which uses Yb-doped photon crystal optical fiber as gain medium, to attain low time interference and high space interference, belonging to the technique of wide-band optical fiber light source and optical fiber sensing. Wherein, the pump semi-conductor laser, lens coupling system, dichroic mirror, Yb-doped large mode-area dual-envelope photo crystal optical fiber and collimation lens are arranged to form dual-range forward or backward output device; compared to general high-power optical fiber ultra-fluorescence light source, the invention has simple structure, better time stability, high incline efficiency, high output power, flat spectrum, and wider band width. The invention can be used in optical fiber sensing, optical fiber top, and optical tomography, etc.