The discrimination problem of the active decoy and radar target is studied based on the full polarization measurement radar system in. Firstly, the polarization characteristic of the active decoy is analyzed under the condition of which antenna polarizations are circular polarization and linear polarization. Then, some polarization scattering properties of the radar target are also discussed. The co-polarization and cross-polarization ratio and its characteristics are presented, which can effectively of the polarization characteristic difference between the active decoy and radar target. A novel polarization discrimination proposal of the active decoy and radar target is given. Finally，the feasibility and validity of the discrimination proposal are verified by computer simulation and actual measured data.