Chemical vapor deposition (CVD) method was used to prepare Nb-W binary alloy. The microstructure and mechanical properties of the Nb-W binary alloy were studied by metallographic microscopy, scanning electron microscopy, electron probe spectroscopy and microhardness tests. Results show that the resulting Nb-W binary alloy has the characteristics of a regular angle layered structure, which is mainly composed of columnar crystals with the following composition fluctuations: Nb as the matrix at the connection between the layers with Nb-W solid solution distributed around it. The Nb-W solid solution is used as the matrix in the layer around which the Nb atoms are evenly distributed. Macroscopically, the W atoms mainly form a layer along the crystal growth direction, followed by transition to Nb atoms through the NbW solid solution; microscopically, the distribution of Nb and W atoms shows the characteristics of alternating content. The layered structure of the Nb-W alloy, composition difference between the layers, and overlapping difference of the grain size between the layers were verified by finite element simulation calculations and analysis, which play a significant role in improving the mechanical properties. The CVD forming mechanism and strengthening mechanism of Nb-W alloys were also revealed.