For the inspection technical problems of austenitic stainless steel small diameter thick wall pipe welds in pressurized special equipment, based on NB/T 47013.5-2021 “Nondestructive Testing of Pressurized Equipment Part 15: Phased Array Ultrasonic Inspection” standard requirements, the phased array acoustic field and defect response were calculated using the ultrasonic simulation software CIVA simulation, formulated for φ114 × 9 mm stainless steel small diameter pipe. The same specifications of the special comparison test block were processed and tested, and finally, the same specification of the simulated test tube was actually tested. According to the results, the CIVA simulation technology can replace the special contrast test block or simulation test block for process verification, and save human and material resources; the formulated detection process can effectively detect common defects in stainless steel small diameter pipe welds with high signal-to-noise ratio and high accuracy of defect quantification and characterization. This research result can provide a technical reference for phased array inspection of austenitic stainless steel small diameter pipe welds.