The invention discloses a lifetime prolonging method for a crankshaft bending upsetting forming die. The die of a crankshaft is designed to be of a split-type combined structure, and a crankshaft dieworking part is composed of a plurality of modules of a bending die, a positioning die, a forming die body, an anti-thrust die and the like. The forming die body is formed by inlaying of a die sleeveand a die core, and the structure of a forming party is designed to be two symmetrically-distributed cavities which alternately work to bear the high-temperature and high-loading effects, and meanwhile, the die core part is subjected to strengthening heat treatment. When the die conducts the forming work, firstly, a heated first crank throw blank is put into the one of the die symmetrical cavities, after die assembly, bending upset-extruding forming of the first crank throw blank is finished, then a manufactured piece is taken out, oxide skins in the cavities are blown away through nozzles, and lubricating heat-insulating agents are sprayed into the die cavities. According to the lifetime prolonging method, the crankshaft bending upsetting forming die can continuously work till two thousand or more pieces are manufactured, the production cost is greatly reduced, the production efficiency is improved, the processing working procedure is simple, and the lifetime prolonging method is easyto apply and popularize.