Abstract: In this paper the acoustoclasticity theory and an ultrasonic testing instrument for welding residual stress analysis arc described. The acoustoclasticity stress analysis was applied to measure welding residual stress distributions nondestructivcly in a welded joint. The technique of acoustoclastic stress analysis employed in this paper uses the velocity difference in ultrasonic chcar waves polarized in principal directions by means of the pulse echo overlap method. A new method to evaluate the material anisotropy is proposed. The results arc as follows: the material anisotropy of the weld metal is much stronger than that of the bacc metal; longitudinal residual stress distributions measured by the acoustoclastic technique arc coincident with those obtained by the theoretical analysis.