In order to explore novel pathways for preparing pure tungsten as a plasma?facing material in fusion reactor divertors and related components, this study investigates the correlation between microstructure and mechanical properties of pure tungsten fabricated via selective electron beam melting (SEBM). By employing SEBM, high?density tungsten specimens were produced, enabling an in?depth examination of the mechanism underlying microcrack initiation. Furthermore, both horizontal (X?Y) and vertical (X?Z) planes of the as?built parts were subjected to microstructural characterization and mechanical testing. The findings revealed that the density of pure tungsten fabricated by SEBM reached 99.3%. The corresponding Vickers hardness attained values as high as 430.44 HV0.3, while the compressive strength was measured to be up to 1790 MPa. Observations of the horizontal plane indicated that the dominant microstructural features were polygonal, cell?like grains; in contrast, the vertical plane exhibited elongated, columnar grains. Fracture surface analysis showed a river?like morphology, representing a characteristic brittle fracture mode.The anisotropic nature of the microstructure gave rise to observable differences in performance. Microcrack formation was predominantly attributed to the recurrent thermal cycles inherent in the SEBM process, which induced pronounced thermal gradient stresses. Consequently, dislocation movement and rearrangement occurred near subgrain boundaries, culminating in local stress concentrations that facilitated microcrack formation. In essence, this study underscored the effectiveness of SEBM for achieving near?full?density tungsten components and elucidated how microstructural evolution, driven by repeated thermal cycling, influenced both mechanical properties and failure mechanisms.