Abstract: Austenite stainless steel butt joint shall not undergo phase transformation during solidification. At room temperature, as cast columnar austenite grains exist with coarse grains, which shall result in serious ultrasonic scattering and large attenuation. Columnar grains are anisotropic, and the sound beam shall be distorted when ultrasonic wave propagates in it, resulting in large positioning error. The phased array ultrasonic testing technology is used to detect the austenitic stainless steel butt joint test block by using the dual crystal plane array probe and the single crystal linear array probe. Combined with the CIVA simulation results, it is proved that the phased array ultrasonic testing can realize the detection of austenitic stainless steel weld.