CRTS　(China　Railway　Track　System)　II　slab　track　is　a　vertical　multi-layer　and　longitudinal　anisotropic　strip　system,　which　has　been　widely　constructed　in　China＇s　high-speed　railway.　In　this　study,　an　innovative　optimum　maintenance　strategy　is　proposed　for　CRTS　II　slab　track,　based　on　the　concept　of　time-dependent　system　reliability　and　life-cycle　cost　analysis.　System　limit　state　function　of　the　track　structure　is　constructed　with　consideration　of　important　serviceability　failure　modes.　The　time-dependent　system　reliability　of　the　track　structure　is　investigated　and　utilized　as　the　indicator　of　track　performance,　which　is　estimated　by　an　innovative　outcrossing　method　based　on　the　system　limit　state　function　considering　time-dependent　correlation　among　failure　modes.　At　each　maintenance　time,　all　critical　failure　modes　and　components　are　identified　and　repaired　to　decrease　the　system　failure　probability　under　the　acceptable　level.　Application　of　the　proposed　maintenance　strategy　is　demonstrated　by　a　worked　example　of　a　track　structural　system　on　bridge.　It　is　found　that:　(1)　appropriate　maintenance　strategy　is　important　to　ensure　service　reliability　of　the　track　system　and　extend　the　service　life;　and　(2)　the　proposed　maintenance　strategy　can　be　utilized　to　predict　when,　where,　and　what　failure　mode　for　maintenance　and　it　can　help　to　minimize　the　expected　life-cycle　cost　without　compromising　the　service　reliability　of　the　track　structure.　©　2023　Institution　of　Structural　Engineers