Abstract: Aiming at the difficulties of detecting the internal defects of welded seam in austenitic stainless steel, and at optimizing the detection processse and assisting in the analysis of ultrasonic signals, the sound field simulation and defect response for 80 mm thick austenitic stainless steel were carried out by ultrasonic module in CIVA simulation software. According to the simulation results, the test block was tested with the ISONIC2009 ultrasonic imaging system equipped with the double-sided phased array longitudinal wave probe. It was shown that the results of CIVA simulation were in good agreement with the actual test results, and CIVA software could provide accurate and efficient process guidance for phased array inspection of austenitic stainless steel butt welds, which was to have high application value.