Weather-proof bridge steel with impact absorbing energy at welding coarse-grain heat-affected zone being not lower than 60J at -60 DEG C

The invention discloses weather-proof bridge steel with impact absorbing energy at a welding coarse-grain heat-affected zone being not lower than 60J at -60 DEG C, and belongs to the field of weather-proof steel. The weather-proof bridge steel is prepared from the following chemical components in percentage by mass: 0.04-0.07% of C, 0.20-0.40% of Si, 1.10-1.40% of Mn, less than or equal to 0.012%of P, less than or equal to 0.005% of S, 0.30-0.50% of Ni, 0.35-0.60% of Cr, 0.02-0.12% of Mo, 0.25-0.45% of Cu, 0.03-0.10% of Nb, 0.008-0.020% of Ti, 0.015-0.030% of Al, 0.003-0.018% of Ca, less thanor equal to 0.0005% of B, and the balance of Fe and inevitable impurities. The contents of Nb, Ni, Mo, Si, Cr and Cu in the weather-proof bridge steel meet the proportion that theta is less than or equal to 1.2 and greater than or equal to 0.6, wherein theta is equal to (20Nb + Ni + 5Mo)/(Cr + 2Cu + 4Si). In addition, the invention further provides a preparation method of the weather-proof bridgesteel with the impact abso