The ultrasonic online inspection system integrates multiple testing technologies including conventional ultrasonic testing, phased array ultrasonic testing (PAUT) and time-of-flight diffraction (TOFD), suitable for real-time flaw detection on production lines. The equipment is equipped with multi-channel transmit-receive ports and adopts negative square-wave excitation pulses with flexible adjustment of voltage, pulse width, pulse repetition frequency and delay time. The receiver features wide gain range, low noise and multi-speed bandwidth gears, supporting A/B/C-scan imaging and waveform processing. It realizes real-time internal defect inspection, data acquisition and image display of workpieces. With stable operation and wide adjustable parameter range, it meets the requirements of continuous online non-destructive testing in industrial sites.