This paper addresses the lack of current Chinese seismic-resistant design principles and methods for track structures in the bridge-embankment transition zone of multi-span High-Speed Railway Simply Supported Bridges (HSRSBs), an area prone to high damage risk. To decouple the seismic-resistant design of track structures from bridge structures, the paper introduces the design principle of Negligible Change in Fundamental Frequency (NCF). Building on this principle, the paper proposes an easily implementable design approach called Friction Slab Extension (FSE), which reduces track internal forces by extending the length of the friction slab without requiring additional seismic-resistant equipment. Through numerical seismic simulations validated by experimental data, the effectiveness of FSE in reducing internal forces in the track of the bridge-embankment transition zone is confirmed. The study also determines the Recommended Length of Friction Slab (RLFS) for practical engineering implementation based on the response reduction limit. Seismic vulnerability analyses demonstrate that adopting the FSE with RLFS effectively mitigates the risk of track structure failure, evidenced by a 15 % reduction in exceedance probabilities under considerable levels. Importantly, this approach ensures that the seismic performance of the bridge components remains unaffected, in line with the expectations of the NCF principle. These findings underscore the efficacy of the FSE and the rationality of the NCF principle, offering valuable guidance for future design developments.