Disclosed is a twin-robot testing apparatus for non-destructive testing. The apparatus comprises two robots (1) for detecting a workpiece (3) from front and back sides thereof; a water circulating unit, comprising a pressure pump, two water ejection coupling probes (2) and water pipes, for providing a coupled water column; an ultrasonic transmitting/receiving device, comprising two ultrasonic transducers, a pulse transmitting/receiving card, and a high-speed data acquisition card, wherein the two ultrasonic transducers are respectively attached at the end-effector of the two robots (1), for transmitting ultrasound and receiving ultrasound respectively, the ultrasonic pulse transmitting/receiving card and the high-speed data acquisition card are mounted on the robot controller mechanism for transmitting and receiving, and acquiring pulse signals, the two robots perform a synchronous transmission testing, with ultrasound transmitted by one robot being received by the other robot, and the ultrasonic transducers are adjusted in position and gesture with the change in the surface shape of the workpiece (3) such that the incidence direction of ultrasonic beam is always in coincidence with the normal direction of the curved surface. The apparatus is used for automatic non-destructive testing of a curved-surface workpiece made of a composite material, and can improve the accuracy, sensitivity and efficiency of the testing.