In order to study the effect of heat treatment on the impact energy of highstrength beam steels, SEM, TEM and EBSD were used to analyze the impact properties of 700L steels with different heat treatment. Results indicated that heat treatment process had a significant effect on the impact properties of 700L steels. When annealed below 400 ℃, the impact properties of the steel were improved. When annealed above 550 ℃, the microstructure of the steel changed slightly and there were considerable amounts of cementites precipitated along the grain boundary, leading to the deterioration of the impact properties. After aircooling treatment at different austenitizing temperatures, the steel treated at 850 ℃ had the best impact properties, which consisted of fine equiaxed ferrite and M/A islands. Texture results indicated that the original steel obsessed strong texture of {001}〈110〉, which might be unfavorable to the impact properties. After mild temperature annealing treatment, the strength of {001}〈110〉 texture weakened, while after austenitizing treatment, the texture disappeared.