Abstract: Considering the volume examination requirements of the fillet weld (BOSS weld) in stainless steel pipeline of nuclear island and combining with the phased array ultrasonic examination experience of carbon steel pipeline butt weld of conventional island (CI), this paper aims to carry out phased array ultrasonic examination simulation analysis for the typical BOSS weld of the primary circuit of the nuclear power plant by using ultrasonic simulation software and to finalize the technical program of phased array ultrasonic examination. The simulation analysis result of specimen shows that phased array ultrasonic examination can effectively examine different types of defects, and the phased array ultrasonic examination process development of stainless steel BOSS weld in future could be based on experimental research results of this paper.