The invention relates to a multi-roller mill backing roller integral repairing method, which includes steps of: selecting, assembling and grinding, wherein bottom surface of a base plate (26) of a backing roller is used as installation standard, the backing roller to be repaired is integrally installed on a grinding processing standard surface of a reconditioning mold. The invention also relates to a multi-roller mill backing roller integral repairing device, which includes a mold arranged on a workbench (21). The mold comprises a fixed base (1) for supporting the backing roller to be repaired, the fixed base is provided with a compaction roller driving device with a power machine and a transmission mechanism and compaction devices which has same number with bearing roller on the backing roller and are arranged at one side or two sides of the backing roller to be repaired, a groove (29) which is adapted with shape of the base plate of the backing roller is arranged at upper end of the fixed base (1), and the groove is in V shape or circular arc shape. The invention can carry out integral gapless grinding for the backing roller to be repaired, realizes integral moulding grinding, and has advantages of simple process, high precision and low cost.