Thin-wall parts of 316L alloy are fabricated with different Z-increments using the powder-feeding laser metal deposition technology. The microstructure and mechanical properties such as the grain size, re-melting depth, and anisotropy of the tensile property of the thin-wall parts are explored at different positions. Moreover, the grain morphologies and growth directions of a single-pass cladding layer and the thin-wall parts are investigated. Based on the microstructure with different Z-increments, the tensile strength and elongation in different directions of the thin-wall parts are analyzed. The results demonstrate that for different Z-increments, the grain morphology of the thin-wall part is mainly columnar, which differs from that of the single-pass cladding layer. In addition, the growth direction of the columnar grain is different in different regions. There is a nonlinear relationship between the Z-increment and the grain size. The growth direction and size of the columnar grain of different Z-increments affect the anisotropy of the tensile property of the thin-wall parts.