Nanostructured surface layer was synthesized on Zr-4 alloy surface by surface mechanical attrition treatment (SMAT), and then the alloy was annealed at different temperatures in vacuum. The effects of the annealing temperature on the thermal stabilities of microstructure and hardness, and the effect of annealing on corrosion resistance were investigated by means of optical microscope, X-ray diffraction, the transmission electron microscope, microhardness test and electrochemical testing. The results show that when the annealing temperature is below 350 oC, the microstructure, grain size and microhardness of surface nanocrystallized Zr-4 alloy have good thermal stability. The corrosion resistance in 1 mol/L H2SO4 solution for the alloy only after SMAT is decreased. However, after further annealing below 350 oC, its corrosion resistance is improved, which is better than that of Zr-4 alloy without SMAT treatment