In　this　study,　an　innovative　dynamics　model　of　LFS　(longitudinal　vehicle　full-speed　cruise　system)　is　developed　by　lumping　the　dynamics　of　a　controlled　vehicle　and　an　inter-vehicles　together.　On　account　of　the　external　disturbance,　parameters　uncertainty　and　the　nonlinearity　within　LFS,　a　DDRC　(disturbance　decoupling　robust　control)　method　is　proposed.　For　this　method,　the　theory　of　NDD　(nonlinear　disturbance　decoupling)　is　utilized　firstly　to　separate　the　external　disturbance　from　certain　part　of　the　proposed　dynamics　model.　Then,　the　invariance　over　the　sliding　mode　of　VSC　(variable　structure　control)　is　used　to　eliminate　the　influence　of　remaining　uncertain　part.　Finally,　the　DDRC　method　is　adopted　to　design　an　LFS　ACC　(adaptive　cruise　control)　system,　and　some　numerical　simulations　are　carried　out　to　validate　its　performance.　The　simulation　results　demonstrate　that　the　proposed　control　system　not　only　exhibits　an　expected　dynamic　response,　high　tracking　accuracy　and　a　strong　robustness,　but　also　achieves　a　global　optimization　by　means　of　a　simplified　control　structure.