Abstract: In order to explore the influence of the remaining coal pillar in the upper coal seam on the stress of the floor and the reasonable layout of the mining roadway in the lower coal seam, taking Tangshangou Coal Mine as the research object, the theoretical analysis and numerical simulation methods and a variety of influencing factors were used to construct the collaborative bearing structure model of the remaining coal pillar and the hinged rock block in the upper coal seam and the stress transfer calculation model of the floor, and the stress and influencing factors of the floor under the remaining coal pillar in the upper coal seam are studied. The research shows that the influence of the remaining coal pillars in the upper coal seam on the stress of the floor is mainly vertical stress, and the influence degree decreases with the increase of floor depth. The stress-increasing area of the floor under the remaining coal pillar is ellipsoidal. The influencing factors of the stress-increasing area of the floor are analyzed, and the quantitative relationship between the influence of different factors on the range of the stress-increasing area is obtained. The peak stress of the coal pillar plays a decisive role in the distribution of the stress-increasing area of the floor. According to the stress distribution of the floor and the results of theoretical calculation and numerical simulation, it is determined that the reasonable stagger distance between the 8 coal pillar and the 11⁻¹ coal mining roadway in Tangshangou Coal Mine should be 20—25 m. This study reveals the stress transfer mechanism of the lower floor of the coal pillar left in the upper coal seam, clarifies the distribution and influencing factors of the floor stress increase area, and obtains the determination method of the reasonable stagger value of the roadway-coal pillar, which can provide a theoretical basis for the reasonable layout of the lower coal seam mining roadway.