Abstract: Tungsten（W） matrix composites are widely used in aerospace, nuclear industry, medical equipment,electronic devices and other fields because of their excellent comprehensive properties, such as high melting point,excellent mechanical properties, low coefficient of thermal expansion, high hardness, good thermal conductivity and excellent corrosion resistance. Aiming at the bottlenecks of the traditional powder metallurgy process for the preparation of tungsten matrix composites, such as limited structural design and difficulties in performance enhancement, the present study utilizes the advantages of the high degree of freedom in structural design of selective laser melting（SLM） technology for the preparation of tungsten matrix composites. In this work, the effect of laser bulk energy density on the phase of W-Y₂O₃ tungsten matrix composites was first investigated. The effects of surface morphology and internal microstructure evolution behavior of W-Y₂O₃ tungsten matrix composites were also investigated. The defect formation mechanism of SLM-formed W-Y2O3 tungsten matrix composites was elucidated.The results showed that the optimization of SLM process parameters can inhibit the formation of defects such as unmelted spherical powder, pores and surface unevenness, but still cannot inhibit the emergence of cracks in tungsten matrix composites. The high-temperature gradient and thermal stress introduced by the SLM process and the high ductile-to-brittle transition temperature of tungsten can induce crack initiation and expand along the grain boundaries of tungsten with low bonding strength to form network cracks. This study not only provides a theoretical basis for the formation mechanism of defects in SLM-formed tungsten matrix composites, but also provides technical support for the preparation of tungsten matrix composites without defects by additive manufacturing.