The invention discloses a method for synchronously constructing vehicle slopes and floor structures in reverse construction. The method comprises the following steps: (1) a floor B0 and a floor B1 of a basement structure are constructed in sequence; and temporary supports are arranged on a top plate according to the stress demands; (2) a lower-layer earthwork is excavated; and meanwhile, a vehicle slope on the floor is constructed in the floor B1 structure; (3) the steps (1) to (2) are repeated until a vehicle slope from a floor Bn-1 to a floor Bn-2 is constructed; and (4) a basement baseplate is constructed; and then, a vehicle slope on a bottommost floor of the basement structure is constructed. The method for synchronously constructing the vehicle slopes and the floor structures in reverse operation solves the difficulty that the basement structure is difficult to synchronously construct with side walls of the vehicle slopes in reverse construction, realizes synchronous reverse construction of the vehicle slopes and the basement structure, is early in forming time of the vehicle slopes, is easy to guarantee the progress, and prevents such difficulties as support replacement, drilling away of support beams and outward conveying of waste concrete caused by reverse construction of the basement and forward construction of the slopes through conventional methods.