Fe-Mo functionally graded materials (FGMs) with different composition-change rates from 100% 304 stainless steel to 100% Mo along the composition gradient direction were prepared by electron beam-directed energy deposition (EB-DED) technique, including three samples with composition mutation of 100%, composition change rate of 10% and 30%. Results show that the composition-change rate significantly affects the microstructure and mechanical properties of the samples. In the sample with abrupt change of composition, the sharp shift in composition between 304 stainless steel and Mo leads to a great difference in the microstructure and hardness near the interface between the two materials. With the increase in the number of gradient layers, the composition changes continuously along the direction of deposition height, and the microstructure morphology shows a smooth transition from 304 stainless steel to Mo, which is gradually transformed from columnar crystal to dendritic crystal. Elements Fe, Mo, and other major elements transform linearly along the gradient direction, with sufficient interlayer diffusion between the deposited layers, leading to good metallurgical bonding. The smaller the change in composition gradient, the greater the microhardness value along the deposition direction. When the composition gradient is 10%, the gradient layer exhibits higher hardness (940 HV) and excellent resistance to surface abrasion, and the overall compressive properties of the samples are better, with the compressive fracture stress in the top region reaching 750.05±14 MPa.