Abstract: Ultrasonic A-scan and C-scan testing combined with metallographic detection was carried out for a composite material containing thermoplastic yarn layer board which was manufactured by resin transfer molding (RTM) process. The difference of ultrasonic testing results between RTM forming process layer board with or without thermoplastic materials was analyzed. The aim of the research is to establish ultrasonic detection method and characteristics of carbon fiber composite material defect judgment method suitable for this kind of material. The result shows that the contact ultrasonic reflection method can effectively and directly reflect the internal quality of the layer board, and it is consistent with the metallographic detecting results.