The towed radar active decoy (TRAD) is a serious threat to the combat effectiveness of radar-guided missiles. In order to improve the anti-TRAD ability of radar seekers, this paper proposes a target tracking method for polarization MIMO radar seekers based on polarization invariants. The method is based on the differences in polarization invariants between the jamming signal transmitted by TRAD and the carrier aircraft echo signals, and achieves identification and tracking for the carrier aircraft through dual-gate tracking. Simulation experiments confirm the feasibility and effectiveness of the method.