Herein, the finite element method (FEM) is used to simulate a single-layer and multi-track temperature field considering the powder-to-solid transition and latent heats of melting at different scanning speeds. The generation of defects, anisotropy of microstructure, and mechanical properties are experimentally analyzed. Results show that increasing the laser scanning speed tends to reduce the wettability of the liquid phase and increase porosity. Moreover, the depth and width of molten pool gradually decrease, which hinders the formation of good metallurgical bonding. Numerous cellular and dendrites are formed in the molten pool, and the high temperature gradient tends to induce planar or cellular dendrites, while the low temperature gradient tends to induce dendritic dendrites. The simulation also demonstrates that the average grain size, grain orientation, strain distribution, and the distribution of the boundary-misorientation angle on the cross-section and longitudinal section show some differences owing to differences in the temperature gradient along different directions. Furthermore, the transverse samples display a higher yield strength, but the ductility is significantly lower than that of vertical samples containing elongated columnar grains along the building direction.