<p>Regarding the limitation that the Hoek–Brown failure criterion fails to account for the anisotropy of stratified rocks—widely used in geotechnical engineering systems such as mining, tunneling, and water conservancy projects—this study employed a Gaussian function to quantitatively characterize the influence of inclination on the Hoek–Brown parameter <i>m</i>_i, proposing a modified Hoek–Brown failure criterion for stratified rocks that is simple in form with clearly defined parameters. It was then validated using triaxial compression test results from various stratified rock types including phyllite, sandstone, slate, and schist with varying inclinations and confining stresses, demonstrating high accuracy in predicting peak compressive strength with 93.6% of data, and showing absolute percentage error within 15%. On this basis, the Weibull distribution function was introduced to describe the random strength of rock microelements, a rock damage evolution model was derived, and a segmented damage constitutive model was established to reflect the complete stress–strain response of stratified rocks including crack closure, elastic deformation, damage accumulation, post-peak softening, and residual strength stages; the theoretical stress–strain curves for stratified rocks with different inclinations under confining stresses ranging from 5 to 20 MPa exhibited high consistency with experimental data, with correlation coefficients mostly exceeding 0.95, validating the model’s effectiveness. Finally, sensitivity analysis clarified the effects of key parameters including Weibull parameters as well as modified Hoek–Brown parameters on the theoretical curve shape, providing practical guidance for parameter calibration in engineering applications and establishing a reliable link between the microstructural anisotropy of stratified rocks, their mechanical behavior under loading, and macroscopic engineering performance.</p>