The effect of rapid hot extrusion on the microstructure and mechanical properties of fine-grained (10~20 μm) 93W-4.9Ni-2.1Fe, fine-grained 93W-4.9Ni-2.1Fe+0.03%Y and traditional coarse-grained (40~45 μm) 93W-4.9Ni-2.1Fe alloy was investigated. The results show that after rapid hot extrusion, the comprehensive mechanical properties of the alloys are significantly enhanced compared with the as-sintered alloys. The initial grain size has a profound effect on the mechanical properties of as-extruded alloys. With the same extrusion processing parameters, the ultimate tensile strength (UTS), elongation and hardness of the as-extruded fine-grained 93W-4.9Ni-2.1Fe+0.03%Y alloy reached 1570 MPa, 6.5% and 45.2 (HRC) respectively. However, the ultimate tensile strength (UTS), elongation and hardness of the as-extruded coarse-grained alloy were 1260 MPa, 5.6% and 39.1. Microstructure observation shows that compared with the traditional coarse-grained alloy, the fibrous degree of the as-extruded fine-grained alloy is much larger under the condition of the same deformation degree. Moreover, the aspect ratio of the tungsten particles in the as-extruded fine-grained 93W-4.9Ni-2.1Fe+0.03%Y alloy achieves 6.8, which is one time larger than that of the as-extruded traditional coarse-grained alloy. TEM shows that after hot extrusion, many subgrains could be observed in fine-grained tungsten phase and numerical dislocations tangled in coarse-grained tungsten phase. In addition, the dislocation density of both kind of matrix is low because of sufficient dynamical recovery-recrystallization.