Abstract: In order to improve the ultrasonic flaw detection rate for the inserted fillet welds, a testing method of linear scanning of rigid phased array from tube seat and flexible phased array from inner wall of nozzle is presented in this paper. Thus, the sound beam full coverage detection of this kind of welds can be realized. Firstly, the influence of different detection planes on the rate of flaw detection is discussed. Then, the CIVA software is used to simulate and analyze the detection of different flaws by two testing methods. Finally, the test of self-designed inserted fillet welds specimen is carried out. The experiment result shows that the rate of flaw detection can be improved effectively by using these two methods at the same time.