This study addresses the significant impact of interrupted-sampling repeater jamming (ISRJ) on linear frequency modulated radar target detection performance by introducing a novel anti-jamming technique grounded in wavelet packet decomposition. The proposed method innovatively constructs a jamming suppression framework based on invariant feature extraction, leveraging waveform prior information of radar signals. This approach overcomes the limitations associated with traditional strategies centered around “jamming parameter estimation + jamming suppression”, which are prone to loss of target information. Experimental results indicate that the method demonstrates superior capability in preserving target information under conditions of low jamming-to-signal ratio, high overlap of jamming and target signals, and complex jamming scenarios, outperforming conventional time-domain and time-frequency domain methods by achieving target information loss of less than 1.67%. The method significantly enhances target detection accuracy, showing robust performance in complex jamming environments and effectively mitigating ISRJ-induced jamming, thus exhibiting substantial application potential.