Prepreg is used as the raw material for the preparation of carbon fiber reinforced plastic （CFRP）， and its quality will directly affect the performance of the finished material. Eddy current detection technology is applied to the damage detection of prepreg. Aiming at the problem that the eddy current in the prepreg is small， the damage signal is more likely to be lifted off by the transmit-receive （T-R） probe composed of double circular coils， and the probe is not sensitive to the damage direction detection， we design a rectangle-circular （R-C） probe. In theory， no matter how the probe is lifted off， it will not affect the received signal. Through three-dimensional electromagnetic finite element simulation， the size of the rectangular coil is optimized and the feasibility of the R-C probe is verified. Experimental research shows that compared with the original T-R probe， the lift-off effect of the R-C probe is significantly reduced and it has a good characterization of the fiber bending direction on the prepreg， and it also has a unique characterization method for cracks； but the signal received under the same excitation is smaller than the original probe.