In this work, a novel magnetic-field-driving approach is proposed and utilized to efficiently enhance the mechanical properties of selective laser melting Ti-6Al-4V. The microstructures of the as-built and the SLM specimens annealed at 400°C, 800°C below the β transus, and 1200°C above the β transus for 30 minutes in the high magnetic field of 7 T are comprehensively characterized in terms of X-ray diffraction, optical microscope, scanning electron microscope, and atomic force microscope. Lattice distortion induced by Al and V atoms are characterized by bonding charge density, providing an insight into the atomic and electronic basis for the solid solution strengthening mechanism and the martensitic transformation mechanism. Referring to the as-built speciments, the ultimate tensile strength and the elongation of annealed specimens at 400 °C and 1200°C in 7T high magnetic field were increased due to the short annealing time. Based on the coupling effect of force field induced by the heat and magnetic, it is expected that the microstructures of SLM Ti-6Al-4V would be conventionally optimized through changing the phase transformation thermodynamics. The validation of this hypothesis will pave a path to develop a novel magnetic-field-driving approach efficiently enhancing the mechanical properties of additive manufactured materials.