Excellent ductility is a critical factor influencing the formability of alloys. While eutectic high-entropy alloysexhibit good casting performance, their limited ductility limits their practical application. Therefore, hot rolling andannealing processes were utilized to address the ductility issue of eutectic high-entropy alloys, and the impact of differentannealing temperatures following hot rolling on the microstructure and mechanical properties of the Al21.5Co19.5Fe9.5Ni50eutectic high-entropy alloy was investigated. The findings indicate that at an annealing temperature of 700 ℃, the alloyachieves optimal fracture strength and elongation at break values of 1 211 MPa and 14% , respectively. The superiorstrength and plasticity combination is attributed to the emergence of a significant number of dislocations in the FCC phaseand their accumulation at the phase interface during the tensile deformation process of the hot-rolled 700 sample. The highlocal stress at the phase interface in the B2 phase induces stress-induced martensitic transformation into L10 twinmartensite, enabling the alloy to exhibit a TRIP effect, thereby achieving an optimal strength and plasticity balance.