The nanocrystalline powder of W-Ni-Fe alloy used for Metal injection Molding(MIM) has been studied. The nanopowder prepared by Mechanical Alloying(MA) was mixed with a wax-based binder to form a feedstock. The effects of MA milling time, nanopowder volume fraction and temperature on the rheological behavior of the feedstock are discussed. With increase of milling time, the viscosity of the feedstock and the sensitivity of viscosity to shear strain rate decrease. Therefore, the fluidity and formalization of this powder feedstock at the condition of long time milling become better. With increase of powder volume fraction, the viscosity of the feedstock has a non-linear increase, which follows the formula: . Here n is equal to 0. 68. The change of viscosity with temperature and shear strain rate is small for the MA powder, so the quality of these MIM products is not strongly effected by the changes of temperature and injection speed.