Abstract: The floor heave failure of small coal pillar roadways involves multiple disciplines, with numerous coupled influencing factors, and the current understanding of its failure mechanism remains incomplete. Existing studies have limitations in explaining floor heave phenomena under complex geological conditions and mining processes. To address these issues, theoretical analysis and numerical simulation were used to investigate the failure mechanism of floor heave in small coal pillar roadways. It was found that the actual stress borne by the roadway exceeded the ultimate strength of the floor strata, causing shear and tensile fractures. Under the horizontal thrust of the overlying basic roof fracture structure and the deformation of the coal pillar, the floor experienced complex stress. Large shear stress occurred at the contact surfaces between the floor and both sides of the coal pillar base, and together with the weak floor strata, jointly contributed to the occurrence of floor heave. Based on the failure mechanism, a targeted technology of "flexible formwork wall gob-side entry retaining + blasting pressure relief + floor lifting + bottom corner anchor cable + concrete paving and solidification" was proposed. The flexible formwork wall gob-side entry retaining helped share the load of the overlying strata borne by the small coal pillar and transferred the stress originally concentrated on the roadway floor to the flexible formwork wall and surrounding rock. Blasting pressure relief at the floor corner dispersed stress and reduced stress concentration. Floor lifting removed debris and restored the roadway section, providing space for support. The bottom corner anchor cables were embedded into stable strata to resist floor heave. The concrete paving and solidification formed a bearing layer, improving the shear and compressive strength of the floor. Field application results showed that the amount of floor heave decreased by 92.04% after adopting this technology, and almost no deformation occurred on the surface of the flexible formwork wall.