A method for producing hydropower steel with thin specification and low sensitivity to weld cracks belongs to the technical field of manufacturing of low-alloy steel. The steel comprises the following components by weight percent: 0.04-0.07 percent of C, 0.10-0.40 percent of Si, 1.10-1.60 percent of Mn, 0.18-0.4 percent of Ni, 0.01-0.02 percent of Ti, not more than 0.30 percent of Mo, not more than 0.012 percent of P, not more than 0.006 percent of S, not more than 0.03 percent of Nb, not more than 0.3 percent of Cr and the balance of Fe and inevitable impurities. The production process comprises the following steps of heating a steel billet, dephosphorizing with high-pressure water, roughly rolling in a recrystallization zone, precisely rolling in a non-recrystallization zone and tempering. The method for producing hydropower steel with thin specification and low sensitivity to weld cracks has the advantages that the comprehensive mechanical property of a steel plate is greatly improved, the production cost is reduced effectively, the excellent low sensitivity to weld cracks is obtained and the mass production is applicable.