The hardness variation of two kinds of alloys with 36 wt pct W content and 7/3, 9/1 Ni-to-Fe ratios during strain aging at 800℃ was studied. The microstructures of the aged alloys were analyzed by X-ray diffraction and TEM. The results show that the strain aging hardness of W-Ni-Fe ternary alloy with 7/3 Ni-to-Fe ratio decreases monotonically with the increase of aging time. Under the same conditions, the hardness of 9/1 Ni-to-Fe ratio alloy decreases in the initial aging stage, but then increases as aging process goes on. X ray diffraction and TEM analysis show that there is not any precipitation depositing from the alloy with 7/3 Ni-to-Fe ratio during aging. The monotonic decrease in hardness of this alloy during aging process results from the recovery, recrystallization and solid solubility declining. In the alloy of 9/1 Ni-to-Fe ratio, the fine β phase precipitates dispersively during aging which hardens the alloy. The two different kinds of mechanisms (the softening one and the hardening one) dec The hardness variation of two kinds of alloys with 36 wt pct W content and 7/3, 9/1 Ni-to-Fe ratios during strain aging at 800 ° C was studied. The microstructures of the aged alloys analyzed by X-ray diffraction and TEM. The results show that the strain aging hardness of W-Ni-Fe ternary alloy with 7/3 Ni-to-Fe ratio decreases monotonically with the increase of aging time. Under the same conditions, the hardness of 9/1 Ni -to-Fe ratio alloy decreases in the initial aging stage, but then increases as aging process goes on. X ray diffraction and TEM analysis show that there is not any precipitation depositing from the alloy with 7/3 Ni-to-Fe ratio during aging. The monotonic decrease in hardness of this alloy during aging process results from the recovery, recrystallization and solid solubility declining. In the alloy of 9/1 Ni-to-Fe ratio, the fine β phase precipitates dispersively during aging which hardens the alloy The two different kinds of mechanisms (the softening one and the hardening one) dec