Different contents of impurity elements such as O, N, S and P of DZ125L superalloy were obtained through ordinary smelting method and purified smelting method, separately. The microstructures of experimental alloy were investigated by optical microscopy and scanning electron microscopy, the mechanical properties of alloy were also measured. Results show that the contents of O, N, S and P of DZ125L alloy can be reduced from 0.0010% to 0.0005% by purified smelting method, and the contents of shrinkage and inclusions are decreased with increment of the purity of DZ125L. The yield strength and tensile strength at room temperature, 760℃, 850℃ and 980℃ are slightly improved in alloy produced by purified smelting method, while the stress rupture properties at 760℃/800MPa, 850℃/560MPa and 980℃/250MPa are improved dramatically. The creep properties at 950℃ and fatigue properties at 760℃ can also be enhanced by purified smelting method.