The invention discloses an error correction method of welding residual stress ultrasonic measurement. The method comprises A, preparing a welded test plate 1 and a welded test plate 2 from a mother material plate of a welded test piece to be detected, B, taking an arcing region sample, a stable region sample and an arc suppression region sample from the welded test plate 1, subdividing the samples according to microstructural difference, and labeling welding feature points, C, labeling welding feature points at corresponding positions of the welded test plate 2, and acquiring a thermal cycle curve by the labeling welding feature points of the welded test plate 2, D, preparing a thermal simulation block E by the thermal cycle curve, E, according to mother material small block and thermal simulation block residual stress measured by an ultrasonic method and a sectioning method, determining a residual stress corrected value, F, according to the residual stress corrected value, correcting an ultrasonic measurement residual stress measured value so that an accurate residual stress value of the welded piece to be detected is obtained. The error correction method can correct errors caused by difference of microstructures of a mother material zone and a zone to be detected and substantially improve residual stress ultrasonic measurement precision.