A new microstructured fiber for low-threshold mid-infrared (mid-IR) supercontinuum generation is proposed and designed. The transmission parameters and mode field intensity are calculated by multipole method. The results show the fiber has high nonlinear coefficient, widely flattened chromatic dispersion, low confinement loss together with a single mode operation in the mid-IR range. It has two zero-dispersion wavelengths(ZDWs) at 2.2 μm and 3.32 μm. The supercontinuum generation in fiber is studied by a split-step Fourier numerical stimulation method. We find the pulse with pump pulse width of 100 fs and peak power of 100 W, can generate the mid-IR supercontinuum spectrum covering 1.5～5.5 μm, bu the energy of pump single pulse is only 10 pJ. Soliton self-frequency shift and dispersion wave amplification are the major reasons for supercontinuum generation in fiber.