A three-layer FEM model, based on the characteristics along the thickness direction of laminated composite metal sheets (LCMS), was developed to study the variation rules of transient deformation in the flexible forming of LCMS using plasma arc. Besides, the comparisons of the typical LCMS Q235A/1Cr13 and single layer metal sheet (SLMS) Q235A were performed. It indicates that the displacement of end point of SLMS is 0.076 mm larger than that of LCMS with the same process parameters. Moreover, the differences of X-axis plastic strain, Z-axis plastic strain along the thickness direction of LCMS decide the bending direction, the occurrence of the edge effect of LCMS during linear heating, respectively. Furthermore, Y-axis stresses of LCMS different layers undergo three dramatic changes with the maximum stress difference of 1.420×107 Pa, and the possible failure of interface delamination occurs in the bonding interface of Q235A and transition layer.