800MPa grade low-welding crack sensitive tempering type hydroelectric steel plate

The invention relates to an 800MPa grade low-welding crack sensitive tempering type hydroelectric steel plate. The steel plate comprises the following components in percentage by weight: 0.09-0.14% of C, 0.24-0.35% of Si, 0.7-1.45% of Mn, less than or equal to 0.013%, less than or equal to 0.002% of S, less than or equal to 0.035% of Nb, 0.012-0.02% of Ti, 0.30-0.50% of Ni, 0.020-0.070% of Alt, 0.035-0.060% of V, 0.25-0.60% of Cr, 0.25-0.55% of Mo, 0.15-0.30% of Cu, less than or equal to 0.0060% of N, less than or equal to 0.00030% of H, 0.0008-0.002% of B and the balance of Fe. The preparation method comprises the following steps: smelting and casting to a cast blank according to set compositions; heating and rolling in two stages; and quickly cooling to temper and thermally treat to obtain excellent strength, plasticity and low-temperature impact toughness which are matched, so that the request on hydroelectric steel is satisfied.