Abstract: The ultimate impact properties of 14Cr1MoR thick plate at 1/2 of the transverse plate thickness at 690 ℃for 24 h after maximum postweld heat treatment in water cooling after rolling and air cooling after rolling methods were studied in detail.The results show that the ultimate impact temperature of water cooling after rolling is -46 ℃, and the average impact energy is 120 J.The ultimate impact temperature of air cooling after rolling is -22 ℃, and the average value of corresponding impact energy is 141 J.From the corresponding metallographic structure, the metallographic structure of water cooling after rolling is quenched bainite, the grain size is 8.5 grade, and the carbide size is about 450 nm.The microstructure by air cooling after rolling is basically bainite, but the microstructure uniformity is poor, some grains are obviously coarse, the grain size is 7 grade, and the carbide size is about 800 nm.