Abstract: To address the issues of residual stress concentration and complex structural deformation induced by severe thermo-mechanical coupling during laser cladding on planar thin plates and curved substrates, and to elucidate the regulatory mechanisms of substrate geometry on the stress–strain distribution within the clad layer, a finite element simulation approach was employed to investigate the stress–strain characteristics of laser cladding on components with different geometric configurations, including planar thin plates and curved surfaces with varying curvatures. The results indicate that when a planar thin plate is subjected to laser heating, the clad layer undergoes melting expansion and compresses the surrounding material; subsequently, the tensile stress generated during solidification shrinkage induces upward warping along the edges of the plate. This warping deformation becomes more pronounced with increasing laser power or decreasing scanning speed. For curved substrates subjected to axial scanning, the stress–strain distribution in the clad layer is significantly influenced by surface curvature. When the convex surface curvature increases from 0.083 to 0.125, the peak von Mises equivalent stress rises from 458.8 MPa to 521.6 MPa, whereas the peak residual compressive stress decreases markedly from 135.4 MPa to 35.4 MPa. In contrast, during cladding on concave surfaces, a stress equilibrium is established due to a "hoop-constraint" effect, resulting in insignificant variations in both the equivalent stress and the peak compressive stress across different curvatures. For curved substrates subjected to circumferential scanning, the equivalent stress in the clad layer diminishes as the curvature increases, and the stress component along the scanning direction exhibits a characteristic distribution of “higher in the center and lower at both ends”. The synergistic interplay between thermo-mechanical coupling effects and geometric constraints imposed by the substrate is the primary mechanism underlying the distinct stress–strain behaviors observed between planar thin plates and curved structures. In planar thin plates, the stress evolution is predominantly governed by rigid constraints, whereas in curved structures, the stress distribution is jointly regulated by geometric curvature and constraint effects.