The characteristics of soliton self frequency shift of ultra-short pulse propagation in fluoride fibers are investigated. Modulation instability, soliton self frequency shift and the dispersive waves generated in the short wavength direction play improtant roles in the spectral evolutions in fluoride fibers when pumped at 1550 nm. The output spectrum is mainly dominanted by soliton self frequency shift when the soliton order of the pump pulse is small. The effects of the length of fluoride fiber, peak power of pump pulse and initial chirp on soliton self frequency shift are discussed. By adjusting the peak power of the pump pulse at 1550 nm, the central wavelength of maximum red shifted Raman soliton can be tuned to above 2.6 μm. Combined with some special rare earth doped fiber amplifiers, a widely tunable fluoride infrared fiber laser can be realized through the method of cascaded Raman soliton self frequency based on soliton self frequency shift effect in fluoride fibers.