To overcome the limitations of complex calibration procedures and low accuracy in light-plane calibration for existing sheet-of-light 3D reconstruction systems, a regional multimodal flexible mapping-based light-plane calibration method is proposed. The proposed method uses the inner corner coordinates of a checkerboard image as control points for light-plane calibration, transforming the problem of solving the light-plane equation during calibration into a mapping problem between control points in the pixel and world coordinate systems. Based on this, a regional multimodal flexible mapping model is constructed to achieve flexible mappings between pixel and world coordinates for feature points in different regions of the light plane. This approach addresses the loss of calibration accuracy caused by distortions, while accounting for non-orthogonal distortions and high-order nonlinear deformations. The method requires only a single comprehensive flexible mapping, achieving both distortion correction and high precision calibration of the optical plane. The method obviates the need for light stripe center calculation and the utilization of intrinsic and extrinsic parameter matrices, thereby eliminating the impact of image-processing errors on calibration outcomes. Experimental results demonstrate that the proposed method is simple to operate and supports a large number of feature points. The average distance residual between corresponding feature points before and after calibration is 0.01 μm. Compared with mapping models of different orders, the mapping accuracy is improved by an order of magnitude. After calibration, the measurement system exhibits a standard deviation of approximately 0.1 μm over multiple sets of 800 repeated measurements, with repeatability accuracy within 8 μm and a root mean square error of 6.5 μm. Compared with traditional invariance of cross-ratio methods, the proposed method improves measurement accuracy by 83.26%. A sheet-of-light 3D reconstruction platform was established. The planar and depth ranges of the system were characterized, and the measurement accuracy in the depth direction was experimentally validated. It fundamentally meets the requirements for stable, reliable, and high-precision sheet-of-light 3D reconstruction systems.