Abstract: Ultrasonic testing is difficult to be implemented well because of the acoustic noise and attenuation resulted by the big column grain in the weld.In the paper,ultrasonic TOFD method is adopted to inspect the defects in austenitic stainless steel weld.Ultrasonic beam with different incident angle is formed in the weld through adjusting experimental parameters,and then the influence of weld structures on amplitude of diffraction waves and signal-to-noise ratio is analyzed to reveal the ultrasonic propagation in the weld.The results indicate that the wave propagation in the weld shows obvious anisotropy characteristics,and the included angle of the ultrasonic beam and discontinuous boundary in weld have a significant impact on the wave attenuation and scattering,so optimizing the beam direction is liable to enhance noise-signal ratio and testing effect.Moreover,the mechanism of anisotropy is presented by constructing weld modal,which gives reliable theory evidence for optimizing testing parameters.