Abstract: Thermoplastic composites have broad development prospects due to their high production efficiency, short molding cycle, long-term use in high-humidity environments, long-term storage of prepregs, and recyclability. This paper mainly reported the ultrasonic evaluation of polyaryletherketone thermoplastic composites, including the comparison of acoustic characteristic parameters and internal quality between thermoplastic and thermosetting composite laminates, the ultrasonic detectability of thermoplastic composite welded parts, and the tracking detection of thermoplastic composite laminates prepared by different processes. The test results showed that the quality of thermoplastic composites could reach the level of thermosetting composite laminates. The sound velocity of thermosetting composite laminates was approximately 3 016 m/s, while that of thermoplastic composite laminates was about 2 858 m/s. The sound attenuation of thermosetting materials was slightly greater than that of thermoplastic materials, with a difference of about 0.5 dB/mm. Thermoplastic composite welded parts were ultrasonically detectable, and defects such as poor welding, delamination within the laminate, and dispersed defects could be detected. The internal quality of thermoplastic composite laminates prepared by the automatic placement + secondary hot pressing process was relatively uniform, while the internal quality uniformity of thermoplastic composite laminates prepared by the automatic placement + oven vacuum curing process was poorer.