The invention discloses a production method of a wide and heavy steel plate with excellent ultra-low-temperature toughness used for offshore wind power, belonging to the technical field of rolling of the wide and heavy steel plate used for offshore wind power through a continuous coasting blank. The production process comprises the steps of: molten iron, converter smelting, LF (Ladle Furnace) refining, RH (Ruhstahl Hausen) vacuum degassing, continuous casting, steel blank check, heating, phosphorous removal, rough rolling, fine rolling, ACC (Activated Calcium Carbonate) water cooling, straightening, cooling in pile, shearing, shot blasting, normalizing, checking and storage. According to the European EN110225 standard, on the basis of the continuous casting blank, through adding micro-alloying elements, such as Nb, V, Ti and the like, and reasonably controlling rolling, a cooling process and a normalizing heat treatment method, the production yield strength is 355-410 MPa, the strength of extension is 470-550 MPa, the coefficient of elongation is 26-36%, the average value of the percentage of contraction of a section in a direction Z is 35-81%, the impact absorbing energy of a core part of the steel plate at ultra-low temperature of -60 DEG C is 100-240 J, and meanwhile, the wide and heavy steel plate has steel with good using performance as well as the thickness is 40-130 mm, and the specification is S355G8+N.