Abstract: An abnormal clutter appeared in a copper alloy during eddy current testing. The causes of clutter were analyzed by means of macroscopic observation, chemical composition analysis, residual stress test, metallographic examination and hardness test. The results show that there was a large residual stress in the material. The residual stress changed the conductivity of the local area on the surface of the material and caused the change of the eddy current detection signal. The residual stress could be reduced by means of stress relief annealing and straightening process adjustment, and the clutter phenomenon in eddy current testing could be improved.