Plastic deformation may occur in metal structure during the manufacturing and service process which will affect the service life of equipment. This study proposes a radio-frequency method resulting from electromagnetic properties variation for metal plastic deformation monitoring. There is a clearly correlation between the macroscopic electromagnetic properties and the plastic deformation of materials. The energy distribution of radio-frequency varies obviously due to electromagnetic properties variation according to the simulation results. Meanwhile, the reflection features are mainly affected by permeability and electric conductivity of the material. Experiments have been conducted to verify simulation results. The results of the experiments indicate that the reflected radio-frequency signal strength decreases with progressive plastic deformation in metal, which has been in conformity with simulations.