The phenomenon and mechanisms of floor heave in deep gob-side entries were investigated through field observations, theoretical analysis, and numerical simulations. The stress distribution of the surrounding rock under typical conditions was examined. The differential mechanisms of floor heave in deep gob-side entries were analyzed. The main controlling factors of these mechanisms are identified. Based on these findings, pressure relief and control measures are designed and applied in field practice. The results are as follows. The numerical simulation results of stress distribution in the surrounding rock are consistent with field measurements. The extraction thickness and the width of the retained coal pillar are identified as the main factors influencing the differential floor heave. A targeted method for pressure relief and control is implemented in an adjacent working face. The method improves the small coal pillar entry protection by adding blasting holes on the solid coal side of the roof and by optimizing advanced support parameters. The high-stress transmission path in the roof was cut off, and the support density is enhanced. After optimization, the maximum displacement of the entry floor from 0 m to 50 m ahead of the working face decreased from 608 mm and 352 mm to 130 mm and 76 mm for Condition I and Condition Ⅱ, respectively. The average displacement decreased from 450 mm and 202 mm to 73 mm and 51 mm.