Solid–liquid–solid twin-roll casting (SLS-TRC) and liquid–solid–liquid twin-roll casting (LSL-TRC) are two processes for manufacturing three-laminated aluminum composite plates by using solid–liquid cast-rolling composite technology. In order to study the variation law of thickness fractions, a 1060/3003/1060 three-laminated aluminum composite plate was taken as the manufacturing product, and the thickness of the solid strip was used as the variable. Based on the “uactive” user subroutines of MSC.MARC software, the 2D thermomechanical coupling models of SLS-TRC and LSL-TRC were established respectively, and the thickness variation law of the solid strip under the two processes was obtained and verified by experiments. Finally, the recommended process was given according to the target thickness fraction. The results show that with an increase in the cladding thickness, the KISS point (complete freezing point of molten metal) of the SLS-TRC process increases, the coordinated deformation position decreases relative to the KISS point, and the strain increases. In the LSL-TRC process, as the thickness of the core increases, the KISS point increases, the coordinated deformation position decreases relative to the KISS point, and the strain decreases. The formation process of the composite interface of the two processes is consistent with the N. Bay theory. Finally, through the comparison of cast-rolling forces, it is found that when manufacturing a three-laminated aluminum composite plate with a relatively small thickness fraction (the thickness fraction is less than 30%), the SLS-TRC process requires less load; when the thickness fraction of the three-laminated aluminum composite plate is large (the thickness fraction is greater than 30%), the load required for the manufacturing of the LSL-TRC process is small. The results of this research can provide practical guidance for the manufacturing of three-laminated metal matrix composite panels.