Abstract: Ultrasonic TOFD testing of stainless steel weld is deeply influenced by the acoustic noise and attenuation produced by the weld structure, and which are the key problem needed be solved. Ultrasonic beams with different incident angle were formed, and the amplitude and noise-signal ratio of diffraction wave influenced by weld structure were analyzed to reveal the characteristics of ultrasonic propagation in the weld. The results indicate that the ultrasonic propagation in the weld show obvious anisotropy characteristics, and the incident angle of the ultrasonic beam and columnar crystal boundary in weld have a significant impact on the wave attenuation and scattering. Moreover, the mechanism of anisotropy was presented by constructing weld model, which gives reliable theory evidence for optimizing testing parameters in real testing. And then, there are two testing methods include primary wave testing method and secondary wave testing method presented to achieve better testing results.