Protective layer mining serves as a fundamental regional measure for mitigating coal and gas outbursts. Establishing a theoretical model to characterize the stress-relief effect is essential for the scientific determination of mining parameters and accurate prediction of the stress-relief outcomes. This study employed an integrated methodology encompassing theoretical analysis, numerical simulation, and field monitoring. Building upon a systematic identification of key factors influencing pressure-relief efficacy during protective seam mining, a theoretical model was developed to characterize the expansion and deformation rate of overlying strata. Using the mining of seam 11 as the protective seam and the subsequent protection of seam 9 at Linhua Coal Mine as the case study, the pressure-relief performance of close-distance protective seam mining was rigorously evaluated through both the proposed theoretical model and calibrated numerical simulations. Based on the project of protecting the 9 coal seam while extracting the 11 coal seam in the Guizhou coal mine, the theoretical model and numerical simulation were used to study the pressure relief effect of the close-protection layer mining, and the influence of different factors on the expansion and deformation law of the overlying strata was obtained. On-site monitoring of the expansion and deformation was carried out, and a comparative analysis was conducted with the theoretical solution of the model.The results show that the pressure relief effect of the protective layer mining is mainly influenced by factors such as the mining height of the protective layer, the rock property of the overlying strata, and the distance between the rock layer and the protective layer; as the 11 coal working face advances, the overlying stratum structure presents the characteristics of "collapse - fracture development - fracture compaction", and the expansion deformation rate of the 9 coal has an evolution law of "slow growth - sharp increase - stable state"; the expansion deformation rate of the protected layer is linearly positively correlated with the mining height of the protective layer, and decays in a logarithmic function form with the increase of the coal seam spacing; the average value of the expansion deformation rate monitored on site is 14.8‰, which is highly close to the analytical solution of 13.59‰ in the theoretical model, verifying the accuracy and reliability of the constructed expansion deformation model.