In order to ensure the welding quality of the butt weld of the supercritical unit pipeline, ultrasonic testing is often used as a nondestructive testing method for the quality evaluation of the butt weld.In this paper, phased array testing technology, Ultrasonic time-of-flight diffraction(TOFD) testing technology and conventional A-type pulse ultrasonic testing technology were used to test the simulated test block. Experiments showed that the three methods can effectively detect slag inclusion, incomplete penetration and cracks. TOFD inspection technology had certain advantages in measuring the height of defects. Phased array ultrasonic testing technology had more intuitive test results. Combined with A-scan signal, it had certain advantages in defect characterization. Conventional A-type pulse ultrasonic testing technology has certain advantages in operability, and can effectively detect complex parts and workpieces.