Residual stresses occur in many manufactured structures and components. Large numbers of investigations have been carried out to study this phenomenon and its effect on the mechanical characteristics of these components. Over the years, different methods have been developed to measure residual stress for different types of components in order to obtain reliable assessment. Nondestructive measurement of residual stress is important to optimize the structures` design and control their mechanical strength. Unfortunately, there is no reliable method that nondestructively gives complete satisfaction in the in situ stress monitoring of the welded structures. Material, geometry, surface quality, cost, and accuracy of the measurement are some of the parameters that must be taken into account in choosing a proper method. Therefore, the development of several methods like X-ray diffraction, incremental hole drilling, and the ultrasonic waves are inevitable. Stress measurement by ultrasonic waves is a nondestructive, easy to use, and reasonably inexpensive method recently used in some industrial applications. Ultrasonic is one of the most economical measurement methods which can be used in the industrial environment. This method is very quick in comparison with the other nondestructive techniques such as X-ray and neutron diffraction that are very expensive and must to do in advanced laboratories by professional users. Recently the critically refracted longitudinal wave technique has become a widely used to measure residual stresses in literature. In this project, after studing the theories, methodology of residual stress measurement using critically refracted longitudinal wave method will be stablished with measuring butt weldments. Taguchi approach is used as statistical design of experiment (DOE) technique for optimizing the four pulsed welding parameters in terms of minimizing the longitudinal residual stresses in austenitic stainless steel 304. These parameters are pulse current, bachground current, % on time and pulse frequency with three levels for using a L 9 orthogonal array of taguchi design. After welding and measuring stresses with critically refracted longitudinal wave technique, the peak stresses were reported in centerline of weldments. These peak tensile stresses had a direct relationship with heat input of welding arc. So that is observed that heat input is the master criterion in analyzing the residual stresses. Analysis of variance (ANOVA) is performed on measured data and S/N (signal to noise) ratios. The optimum condition providing the lowest residual stress and heat input. This condition were found the lowest level of pulse current, background current and % on time and the highest level of pulse frequency. As a result of Taguchi analysis in this thesis, the background current was the most influencing parameter on residual stress and pulse current has the next most significant effect. The % on time is in the third stage and pulse frequency is the last one. The average of these percentage contributions of background current, pulse current, % on time, and pulse frequency in 1.5 and 3 milimetre depth of surface are 51.7%, 29%, 17.7% and 1.6%, respectively. Consequently, the Taguchi method was found to be promising technique to obtain the optimum conditions for such studies. Keywords : Residual stress, critically refracted longitudinal wave technique, Analysis of variance, Design of experiment, pulsed current gas tungsten arc welding (PCGTAW), austenitic stainless steel.