Considering　safety　and　serviceability　simultaneously,　a　comprehensive　system　limit　state　function　(LSF)　model　and　its　application　for　CRTS　II　track　slab　is　analyzed.　First,　a　comprehensive　system　LSF　model　is　proposed,　and　the　procedure　of　comprehensive　system　reliability　analysis　is　developed　from　integrating　the　method　of　moments　with　finite　element　(FE)　code.　Second,　based　on　the　proposed　model,　comprehensive　system　LSF　of　CRTS　II　track　slab　is　constructed,　considering　five　important　safety　failure　modes　and　three　important　serviceability　failure　modes.　Then,　comprehensive　system　reliability　of　a　CRTS　II　track　slab　on　simply　supported　viaduct　is　analyzed　using　the　proposed　method,　and　the　result　is　compared　with　general　system　reliabilities　considering　safety　and　serviceability　separately.　It　is　found　that　the　proposed　comprehensive　system　LSF　model　has　a　flexible　form　and　the　proposed　methodology　can　be　efficiently　applied　for　comprehensive　system　reliability　assessment.　It　is　also　found　that　comprehensive　system　reliability　analysis　is　more　appropriate　compared　with　general　system　reliability　analysis,　and　thus,　comprehensive　system　reliability　results　can　help　to　determine　an　appropriate　maintenance　strategy　and　ensure　the　safety　operation　for　high-speed　trains.