The　accuracy　of　bridge　performance　monitoring　and　evaluation　is　easily　affected　by　unfavorable　factors　such　as　vehicle　coupling　and　test　noise.　In　order　to　accurately　evaluate　the　dynamic　response　and　health　monitoring　threshold　of　the　bridge　under　different　operating　conditions,　a　time-varying　dynamic　vehicle　group　model　including　the　main　uniform　mass　and　the　coupling　mass　was　established,　and　the　influence　of　road　roughness　was　considered　in　the　coupling　equation.　A　bridge　monitoring　strategy　considering　signal　noise　ratio　and　vehicle-bridge　interaction　was　proposed,　and　the　effectiveness　of　the　monitoring　strategy　was　verified　by　taking　a　simple　supported　beam　as　an　example.　The　results　showed　that　the　proposed　time-varying　dynamic　vehicle　group　model　could　accurately　consider　the　influence　of　road　roughness　and　estimate　the　threshold　of　health　monitoring,　and　the　proposed　bridge　monitoring　strategy　could　filter　out　a　large　amount　of　low　signal-to-noise　ratio　or　meaningless　data,　thus　saving　computing　resources　and　realizing　the　lightweight　safety　monitoring　of　bridges.