Abstract: Although cross-sectional warping and longitudinal fibers compression can introduce significant errors in calculating normal stress during beam bending under transverse loading, these errors become negligible when the beam's span-to-depth ratio exceeds 5. A core challenge in teaching mechanics of materials is helping students grasp these specific characteristics of transverse bending. Digital image correlation (DIC)—an advanced optical deformation measurement technique—offers advantages such as non-contact, full-field data acquisition, and operational simplicity. This paper explores teaching reform in three-point bending experiments by integrating the DIC method to visually measure and characterize deformation features under transverse bending. By correlating strain field of beams with varying span-to-depth ratios using the generalized Hooke's law, the normal stress distribution along the cross-section height can be obtained, enabling a more comprehensive understanding of the beam bending normal stress formula. Classroom practice demonstrates that introducing advanced optical measurement methods to visualize key concepts enhances students' understanding of related theories, cultivates integrative and practical skills, and stimulates interest in scientific and technological innovation.