The creep resistance of one kind of Zirconium based alloy with Niobium, Iron, Chromium, Tin alloying elements was investigated, the creep curve ( epsilon-t) was obtained in stress levels of 117MPa, 137MPa, 157MPa respectively by holding 200 hours at 400 degrees C. The results show that the creep resistance of this alloy is much better than that of Zircaloy-4. The microstructure of post- creep test was observed by TEM, which shows that the dislocation morphology is changed from dislocation lines to dislocation cells with strain increasing, and some precipitates grow larger. It is concluded that the creep is controlled by dislocation climb-glide diffusion mechanism.