Method for improving mechanical property of 1800MPa-grade hot forming steel welded joint

The invention discloses a method for improving the mechanical property of a 1800MPa-grade hot-formed steel welded joint, which comprises the following steps of: heating a plate blank in a heating furnace, and then putting the plate blank in a mold for hot stamping; in the die quenching process of hot stamping, temperature compensation is conducted on the welding spot position of a hot forming workpiece, and the cooling speed of the hot forming workpiece is controlled to be 10-30 DEG C/s; temperature compensation is not carried out on non-welding spot positions; when the temperature of the position of the welding spot is reduced to 100-200 DEG C, the plate blank is moved out of the mold for welding; according to the method, a resistance spot welding method does not need to be improved, and only temperature compensation needs to be carried out on the position of a subsequent welding spot during hot stamping, so that the tensile shear resistance and the cross tensile property of the welding spot can be greatly i