Abstract: Zr-4 alloy was heated to 1 000℃ for 5 min, and then was cooled to room temperature at cooling rate of 200, 20, 2, 0.2, 0.02℃·s^-1. The effects of quenching cooling rates on microstructure and corrosion behavior of the alloy in 360℃/18.6 MPa water were studied. The results show that the average width of α phase plate in alloy increased from 1.4 μm to 28.0 μm, and the average particle size of the second phase particles increased from 38 nm to 580 nm with decreasing cooling rate from 200℃·s^-1 to 0.02℃·s^-1. The second phase particles were mainly distributed in grain boundaries of α phase plate at cooling rate of 200, 20, 2℃·s^-1, and were distributed both inside the crystal and grain boundaries at cooling rate of 0.2, 0.02℃·s^-1. When the cooling rate decreased from 200℃·s^-1 to 0.2℃·s^-1, the increase of the second phase particles helped to release the compressive stress in the oxide film and improved the corrosion resistance of the alloy. A number of microcracks initiated around the second phase particles, and the corrosion resistance decreased at the cooling rate of 0.02℃·s^-1. The corrosion resistance was the best at the cooling rate of 0.2℃·s^-1, and the ZrO₂ grains in the oxide film were mainly columnar crystals with dense structure.