The invention discloses a road vibration isolation system for preventing underground spatial structure vibration and a construction method thereof. A steel spring floating plate is arranged between the roof of a building in an underground space and an asphalt pavement as a travelling pavement above the roof, through spring shear stiffness of spring vibration isolators and compression stiffness of flexible water stopping materials at left and right sides of the floating plate, floating plate vertical support and lateral support stiffness is formed, through a shear hinge and the flexible water stopping materials at front and rear ends of the floating plate, floating plate vertical deformation and smooth longitudinal stability without mutation are realized, and the flexible water stopping materials, kerb drainage ditches and longitudinal drainage ditches are arranged so that accumulation of rainwater in gaps between the floating plate and a slope surface layer is avoided and rainwater-caused corrosion damage to the spring vibration isolators is prevented. The road vibration isolation system can prevent road traffic-caused underground spatial structure vibration, has good vibration isolation effects, can reliably work in an outdoor environment for a long time and is convenient for construction.