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To solve the problem of internal surface cracking problem during equal channel angular pressing (ECAP), this study modified a conventional die. The dies before and after modification were compared and analyzed by using DEFORM-3D software. Finally, a modified ECAP die was manufactured to investigate the effect of different number of pressed passes on the microstructure and mechanical properties of the solution-treated Mg93.5Zn2.5Y2.5Mn1Ti0.5 alloy. The results show that the volume fraction of dynamically-recrystallized grains continuously increases while the volume fraction of W phase continuously decreases with the increase of pressed passes. The size of recrystallized grains initially decreases and then increases, reaching the minimum after 6 pressing passes. The basal texture of (0002) initially decreases, then increases and finally decreases, and the basal texture of 6-pass pressed sample displays the strongest texture. The yield strength and tensile strength of the alloy increase initially and then decrease, while the elongation increases continuously. After 6 pressing passes, the alloy exhibits excellent comprehensive mechanical properties, with a yield strength of 251 MPa, a tensile strength of 340 MPa and an elongation of 26.1%.