The invention relates to a construction method for a plate ballast bed of a metro. The method comprises the steps of a basement backward paving construction step, in which a truck mixer transports concrete from a front material feeding well segment to a material storage truck to and fro via a pump or a belt conveyer in a backward moving manner, the material storage truck moves backward to an area to be paved and discharges concrete, and a paver paves; and a plate pathway conveying and paving steps, in which a back pathway and floating plates are transported to a construction area by using a flatcar, a plate paver is used for sequentially discharging the floating plates from the flatcar and paving the same to a predetermined area; and then the pathway is discharged from the flatcar and paved on the floating plates. According to the method provided by the invention, building of a temporary pathway is not needed, the damage to tunnel segments caused by the temporary pathway when the temporary pathway is supported and fixed is reduced, and the construction speed is rapid; in a tunnel, both the truck mixer and the material storage truck can move on a plane as well as a hook face for conveying the concrete, so that the concrete transportation cost is low, and the adaptability is good; the backward paving construction can be operated with subsequent construction in parallel, so that the construction efficiency is high.