In order to improveultrasonic testing capability on austenitic stainless steel weld, ultrasonic propagation characters and related ultrasonic time of flight diffraction method (TOFD) were investigated. The direction of detection beam was changed through adjusting the probes center spacing (PCS) to analyze the signal to noise ratio (SNR) varies with the angle between testing beam and columnar grain. And then, the probe distribution method of primary wave and secondary wave based on ultrasonic TOFD techniquewere proposed. Moreover,the model of wave propagation was constructedtoidentifythe characteristic signal of defect in the light of complex wave structure in secondary wave method. The research indicates that the ultrasonic propagated in the stainless steel weld reflects obvious anisotropy characters, and the angle between columnar grain and detection beam is the main influencing factor to SNR of testing signal. Primary wave method and secondary wave method is respectively adopted for testing, when theprobe is located on the side of weld root and reinforcement. The testing capability on stainless steel weldcan be effectively improved when the angle between detection beam and columnar grain is within the range of 35°~48°and high beam amplitude is obtained. The primary and secondary wave methods of ultrasonic TOFD based on anisotropic characteristic of wave propagation are very important to improve the ultrasonic testing capability on inner defect of austenitic stainless steel weld.