In this paper, the tensile creep behavior in vacuum of W-4Re-0.27HfC alloy prepared by powder metallurgy was studied. The creep temperature was 1500~1700℃ and the creep stress was 40~60MPa. SEM, EBSD and TEM observations were used to observe the microstructure, characterize the evolution of grain size and dislocation during the creep process. The results show that the steady creep rate of W-4Re-0.27HfC alloy ranges from1′10-7~5′10-6, which is two orders of magnitude lower than that of pure tungsten (W). The creep resistance of W-4Re-0.27HfC alloy is higher than that of pure W due to the dislocation pinned by HfC particles and the lattice distortion caused by Re replacing W atoms. The creep mechanisms of W-4Re-0.27HfC is mainly dislocation slip, accompanied by grain boundary slip at 1500℃. Dislocation climb becomes the main creep mechanism with increasing temperature. The dislocations were blocked by the HfC particles, which leads to the debonding of the HfC/ matrix interface. Moreover, the desquamation of HfC particles forms pores, which results in the great degradation in the creep properties of the alloy.