In order to make the spectral width of the mid-infrared supercontinuum spectrum continuously tunable， a chalcogenide photonic crystal fiber （PCF） with As₂S₃ matrix material and LiNbO₃ crystal auxiliary rods， whose optical axis was running along the axial direction of the fiber， was proposed. The influence of the adding electric field with parallel direction of the axis of the fiber on the dispersion， effective mode field area， and non-linearity coefficient was simulated by using the finite element method （FEM）， the evolution of optical pulse transmission in optical fiber was investigated， and the tunability of the axial electric field on the spectral width and coherence of the supercontinuum spectrum was analyzed. The results reveal that the spectral width and tunable range of the supercontinuum spectrum in the fiber with a filling factor of 0.6 is greater than that with other filling factors at the same pump. When injecting a pump pulse with a peak power of 5 kW， a pulse width of 100 fs， and a central wavelength of 3.5 μm into the fiber， the output supercontinuum spectral width reaches 2.242 0 μm for an electric field strength of 40×10⁸ V/m， an increase of 176.30 nm over that without the electric field. As the adding electric field causes the coherence factor of the supercontinuum to converge to 1 at longer wavelengths， it also contributes to the coherence of the supercontinuum. Mid-infrared supercontinuum light sources with continuously tunable spectral width can be obtained and have potential applications in fields such as sensing detection and biomedicine.