In this work, the creep properties of W-4Re-0.27HfC (wt.%) alloy at temperatures of 1800, 1900, and 2000 ℃ was investigated. Combining Scanning Electron Microscopy (SEM), Electron Back Scatter Diffraction (EBSD), Density Functional Theory (DFT), we analyzed the grain size, grain type, dislocation density, fracture morphology, and the mechanism of creep failure of W-4Re-0.27HfC alloy after creep at different temperature. The results indicate that the steady-state creep rates at creep temperatures of 1800, 1900 and 2000 °C are 9.8×10_-6^{/s, 1.0×10}_-5^{/s, and 2.1×10}_-5^{/s, respectively.} With increasing creep temperature, the proportion of low-angle grain boundaries decreases while the proportion of high-angle grain boundaries increases, resulting in an increase in average grain size. During the creep process, grain undergoes plastic deformation, forming numerous ductile dimples. The poor deformation compatibility of high-angle grain boundaries leads to the formation of voids, accelerating creep failure. EDS results illustrates that the HfC particles in W-4Re-0.27HfC alloy oxidizes severely. DFT calculations show that the interface binding energy between HfC and matrix decreases from -11.221 J/m₂ ^to-3.935 J/m₂ ^after HfC oxidation, reducing the strengthening effect of the second phase.