The objective of this research is to develop a method to evaluate important weld dimensions in thin plates by using laser generated ultrasounds and EMAT receiver. The superimposed laser sources (SLS) technique is developed to generate narrowband Lamb waves with fixed wavelengths in thin plates. The method permits the flexibility of selecting desired wavelength. The signal processing procedure that combines wavenumber-frequency (k-w) domain filtering and synthetic phase tuning (SPT) is used to further reduce the complexity of Lamb waves. The k-w domain filtering technique helps to filter out the unwanted wave components traveling at the direction that is not of interest to us and the SPT technique is applied to amplify and isolate a particular Lamb wave mode. The signal processing procedure facilitates the calculation of reflection coefficients of Lamb waves that result from the presence of weld joints. The SLS and signal processing procedure are then applied to measure reflection coefficients in butt welds and lap welds. Two methods, the direct method and indirect method, are used to develop models that use reflection coefficients as predictors to predict these weld dimensions. The models developed in this research are shown to accurately predict weld dimensions in thin plates.