The invention discloses a horizontal reinforced concrete steel pipe pile pre-supporting and protecting method. The method includes the following steps that 1, multiple steel pipe piles are jacked in along a pre-designed outer contour line of an oversized box culvert; 2, after the steel pipe piles penetrate through a roadbed, steel reinforcement cages are placed in the steel pipe piles, and concrete is poured; 3, every two adjacent steel pipe piles are meshed with each other to form a rigid rectangular shed along the outer contour line of the oversized box culvert; 4, construction of the oversized box culvert is carried out. The structural safety performance and durability of the steep pipe piles which penetrate downwards through the box culvert and upwards cross a high speed road are improved, and the method is suitable for supporting and protection of homogeneous waterless roadbed soil layers with long distances, large sections and ultra-thin coverage.