Abstract: To realize the large area fast C scan and the special position C scan of the composite materials,phased array ultrasonic C scan imaging testing system based on the wheel probe and X-Y wire encoders is researched and developed.The experimental results show that the wheel probe C scan testing system,which coupling effect is good and scanning speed is fast,is especially suitable for fast C scan testing of composite materials in the field of aerospace;X-Y wire encoders C scan testing system for specific area,which has the accurate positioning and good repeat coverage,has the big advantage of defect quantification.