Rare earth Y has excellent refining effect on TiB₂ particle reinforced composites, and can improve the performance damage caused by TiB₂ particle clusters. It plays an important role in improving the comprehensive mechanical properties of composites. In this paper, 3% (mass fraction) TiB₂/Al–Zn–Mg–Cu–Zr–Y composite plates were prepared by traditional casting and hot extrusion. The effects of Y content on the microstructure and mechanical properties of TiB₂–reinforced aluminum matrix composites were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile test at room temperature. The results show that the as-cast microstructure of composites can be refined by addition of Y, and the refining effect is the best when 0.1% Y (mass fraction) is added. The composite with 0.1% Y (mass fraction) has the best mechanical properties, with the ultimate tensile strength (UTS) of 729.85 MPa and the elongation (EL) of 8.06%. The addition of Y element leads to the formation of insoluble phase Al₈Cu₄Y(Zr) at the grain boundary, which can be broken and strengthened by hot extrusion. Excessive Al₈Cu₄Y(Zr) leads to the decrease of strength and plasticity of the material. TiB₂ particles can increase the dislocation density in the matrix, and have the effect of dislocation strengthening and load transfer strengthening. GP II and η′ are the main nano-strengthening phases in the T6 state of the composites.