<p>Under the condition of multi-coal seam mining, the remaining coal pillars left by the upper coal seam mining will cause stress concentration phenomena on the floor and the underlying coal seams. To reveal the characteristics of stress propagation in the floor of coal pillars, the stress distributions of these pillars are classified into three categories based on engineering practices: large quasi-elastic coal pillars, medium plastic coal pillars, and small plastic coal pillars. Numerical simulations were conducted considering seven types of strata distributions, followed by a physical model test to validate the results. It shows how the distribution of rock properties affects the stress concentration range and propagation angle in the underlying strata of three coal pillar types. Ultimately, a semi-plane theoretical model based on the Coal-goaf-coal(CGC) structure was developed, and the stress distribution equation for the Coal-goaf-coal-goaf-coal(CGCGC) structure was derived. Under the CGCGC structure, the stress distribution patterns of the three types of coal pillars are similar. Significant stress concentration occurs on both sides of the coal pillars and within the remaining coal pillars. Moreover, under the same in-situ stress, the vertical stress in the floor is the lowest beneath the small coal pillar, followed by the medium and then the large coal pillar. The research results can provide a theoretical reference for the risk assessment of residual coal pillars in multi-coal seam mining engineering.</p>