The　monitoring　strategy　for　bridges　considering　signal-to-noise　ratio　and　vehicle-bridge　interaction　is　proposed　in　order　to　discard　a　large　amount　of　low　signal-to-noise　ratio　data　or　normal　data.　The　composition　of　the　vibration　signal　is　discussed,　and　the　reasonable　and　accurate　monitoring　threshold　should　be　determined　according　to　vehicles-bridge　interaction　dynamics.　A　time-varying　dynamic　vehicle　group　model,　which　includes　main　uniform　parameters　and　coupling　mass,　is　established.　The　dynamic　coupling　equations　for　bridge　and　car　groups　are　established,　and　the　analytical　expression　is　given.　The　health　monitoring　for　a　simply-supported　beam　is　discussed.　The　dynamic　response　under　different　uniform　mass,　speed,　and　vibration　frequency　of　the　car　group　is　analyzed　based　on　the　vehicle-bridge　interaction　theory.　The　monitoring　threshold　is　determined　according　to　simulated　results　and　measured　signals.　©　2014　American　Society　of　Civil　Engineers.