The evolution of microstructures of ZL201 sub-frame during casting was investigated. The processes of casting and cooling solidification were calculated by finite element and thermodynamic theory. The phase compositions were characterized by X-ray diffraction (XRD), and the microstructures were detected by optical microscope (OM) and scanning electron microscopy (SEM). The results show that the simulated results of casting and cooling process are consistent with the experiment. When the pressure is 0.4 MPa, the filling rate of ZL201 sub-frame is 98% and the filling time is 10 s. After heat treatment, the θ phases (Al₂Cu) dissolve into the Al matrix, and form homogeneous solid solution, which increases the grain size.