Abstract: TiB₂/Al-Si composite samples were produced by selective laser melting (SLM), following by different heat treatments. The microstructures and mechanical properties of in-situ TiB₂/Al-Si composites before and after different heat treatments were analyzed by XRD, SEM, electron back-scattered diffraction (EBSD), EDS and tensile tests. The results indicate that the as-prepared SLM TiB₂/Al-Si composites have ultra-fine microstructures and high mechanical properties due to the high cooling rate of SLM and the existence of nano TiB₂ particles. The average grain size is 1.1 μm, and TiB₂/Al-Si composites show high yield strength of 262 MPa, high tensile strength of 435 MPa and excellent elongation of 11.88%. For the TiB₂/Al-Si composites after different heat treatments, the mechanical properties reach its best after the direct artificial aging (150℃/12 h). The tensile strength of the TiB₂/Al-Si composites reaches 488 MPa which increases by 53 MPa, and the elongation decreases to 7.2%.