Abstract: Hydride was prepared on the surface of rolled and annealed Zr-4 zirconium alloy by hydrogen absorption test. The phase compositions of the precipitated hydride were analyzed by X-ray diffractometer (XRD), and the micro-mechanical properties were studied with nano-indentation combined with scanning electron microscope (SEM) observation. The results show that the hydride precipitated in the Zr-4 zirconium alloy was mainly δ-hydride. The fracture toughness K_IC of the δ-hydride was (1.93±0.29) MPa·m^0.5 which was far lower than that of α-Zr phase, the Young's modulus of it was 95.113 GPa which was close to that of α-Zr phase, and the nano-hardness of it was 4.047 GPa which was higher than that of α-Zr phase. So the δ-hydride precipitated in the Zr-4 zirconium alloy is a kind of hard and brittle phase.