The invention discloses a flexible cable prestress scaling ladder bed which comprises two sections or more of single section arm rests which can relatively slide, stretch and contract. The flexible cable prestress scaling ladder bed is characterized in that each single section arm rest comprises two lower chord beam rods, two upper chord tensioning cables, a plurality of stand columns and multiple levels of ladder pedals, wherein the two lower chord beam rods are connected through the ladder pedals, the two upper chord tensioning cables are located above the two lower chord beam rods respectively, the lower chord beam rods and the upper chord tensioning cables located on the same side with the lower chord beam rods are connected through the stand columns, and the upper chord tensioning cables have the smaller elastic modulus than that of the lower chord beam rods and the larger stretch rate than that of the lower chord beam rods. According to the flexible cable prestress scaling ladder bed, the rigid-soft combined ladder bed is adopted, the features of structural materials are fully played, the strength and the rigidity of the ladder bed structure are obviously improved, the total mass of a system is effectively reduced, the work performance of a scaling ladder is improved, and cost is reduced.