In this paper, ZL101-xCr (x=0, 0.1, 0.2, 0.3, 0.5, 0.8wt.%) aluminum alloys were prepared by vacuum electromagnetic induction melting furnace. Using OM, XRD, SEM, EDS and TEM, the microstructures of the experimental alloys with different Cr contents were characterized, and their mechanical properties were tested. The results show that the main phases of the experimental alloy include primary α-Al, (α-Al+Si) eutectic, Al₁₃Cr₄Si_4, α-Al₁₂(Cr, Fe)₃Si₂, and Fe-rich phases (β-Al₅FeSi and π-AlSiMgFe). The microstructure of the experimental alloys after adding trace element Cr is refined. With the increase of Cr content, the α-Al dendrites tend to be equiaxed, the eutectic structure area becomes narrow, and the Fe-rich phase and eutectic Si size become smaller. Al₁₃Cr₄Si₄ and α-Al₁₂(Cr, Fe)₃Si₂ phases are formed in the alloy eutectic structure. Adding Cr element can improve the undercooling degree of the alloy, which has a positive effect on refining the alloy structure. When the Cr content is 0.3%, the microstructure refinement and modification effect and mechanical properties of the cast alloy are the best, and the tensile strength and elongation are 182.88Mpa and 3.38%, respectively