The electron beam freeform fabrication technique has been widely used in aerospace and other fields due to its advantages, such as high material utilization, high energy density and high vacuum environment. Using a GH4169 nickel-based superalloy as the research object, an electron beam freeform fabrication deposition experiment was carried out, and the microstructure was analysed via SEM, TEM and XRD. At the same time, the mechanical properties of the as-deposited sample were tested at room temperature to study the evolution of the microstructure during the deposition process and its influence on the mechanical properties. The results show that the element segregation during the deposition process causes the Laves phase to precipitate along the dendrites, and the heat accumulation caused by thermal cycling results in the precipitation of the γ″ phase around the Laves phase. During the loading stage, the hard and brittle Laves phase breaks to form a crack source, and the fracture mode is microvoid coalescence fracture.