The formation mechanism of linear macro-segregation in Al–Cu–Mn–Ti alloy cylindrical shell casting was studied by characterizing samples by X-ray detection, microscopic examinations, composition analysis, and simulation of the heat transfer of Al–Cu–Mn–Ti alloy cylindrical shell casting in the solidification process. Numerical and experimental results indicated that linear macro-segregation always occurred in the portion of casting connected with the slit gating system, because of the great hot tearing tendency, the hot cracks formed could be fed by the melt through the slit gating system with an excellent temperature gradient and feeding angle. According to significant effect of floatation of lower density α-Al grains, the solute gradient was formed along the vertical direction of the slit gating system. The hot cracks near the bottom of casting were fed by melt with high concentration of Cu and so, they were cicatrized by the eutectic structure/α-Al + Al₂Cu at a temperature of 548℃.