Abstract: Fillet weld is a common form of welding in engineering. However, comparison to butt weld, its special structure and welding type increase the difficulty and complexity of its testing. Based on the analysis of traditional ultrasonic testing, this paper comes up with phased array ultrasonic testing for fillets, and takes T and Y weld joint as example to throw light on the procedure to make testing plan for fillet. The results of the phased array ultrasonic testing of cracks in T and Y weld joints are also displayed to verify the testing plan. This research would provide experience to the application of phased array ultrasonic testing for fillet.