This study introduced a novel magnetic-field regulation method in metallic additive manufacturing to achieve the refined grain structure and enhanced mechanical properties without post-treatment and composition changes. As a showcase material, the Ti6Al4V alloy was fabricated using direct energy deposition under the static magnetic field (SMF). It is found that the transverse SMF of 0.55 T can effectively regulate the microstructure with twisted prior-β grains (strong orientation to weak orientation) and discontinuous α grain boundaries. The tensile test shows a significant improvement of tensile elongation (ε_f) in both longitudinal and transverse directions with a slight strength decrease. GRAPHICAL ABSTRACT IMPACT STATEMENT A magnetic field assisting laser additive manufacturing approach was developed to modulate the microstructure for Ti-6Al-4V alloy. The resulting refined β grains and discontinuous α grain boundaries (GBs) improve the ε_f significantly.