The invention discloses a wavelength tunable intermediate infrared mode-locked fiber laser. The wavelength tunable intermediate infrared mode-locked fiber laser comprises a laser pumping source, a dichroic mirror, a first convex lens, a rare earth ion doped fiber, a second convex lens, a planar blazed grating, a third convex lens and a carbon nanotube saturated absorption mirror which are sequentially arranged along an incident light path, and 3[mu]m middle-infrared band wavelength tunable mode-locked pulse output is achieved. The wavelength tunable intermediate infrared mode-locked fiber laser is simple in structure, excellent in performance and easy to operate, and solves the problem of middle-infrared band wavelength tunable mode-locked pulse output. According to the invention, a single-arm carbon nanotubes with different tube wall diameter distribution are prepared as a saturable absorber, so that the working waveband of the saturable absorber covers the 3[mu]m mid-infrared waveband, the working bandwidth of the saturable absorber is expanded, and the tuning range of the mode-locked laser is enlarged. The scheme for generating the 3[mu]m tunable mode-locked fiber laser providedby the invention has good transportability and expansibility, and the variety and the number of the gain fibers can be flexibly changed according to actual wavelength requirements.