We demonstrated an ultrabroadband supercontinuum (SC) generation with high coherence property in all-normal-dispersion (ANDi) Te-based chalcogenide tapered fiber. The fibers made of Ge20As20Se15Te45 core and Ge20As20Se20Te40 cladding glasses were fabricated via isolated stacked extrusion. The waist diameter and length can be accurately controlled by a homemade tapering platform. When the core diameter of the waist was ≤14 μm, the fiber showed an ANDi characteristic in the wavelength range of 1.7-14 μm. A coherent SC generation covered 1.7-12.7 μm was generated in a 7-cm-long tapered fiber, pumped at 5.5 μm. To the best of our knowledge, this is the first SC experimental demonstration in Te-based step-index tapered fiber and the broadest SC generation in chalcogenide tapered fiber when pumped in the normal dispersion regime so far.