Abstract: For using gob-side entry retaining under the condition of hard limestone roof in thin coal seam of a mine, the mechanical model of roadside soft medium connecting roof is established, theoretical calculation is used to obtain the height range of soft medium, numerical simulation is used to analyze the relationship among the characteristics of roadside support, plastic zone of roadway surrounding rock, deformation of surrounding rock and the height of soft medium, which determines that the height of soft medium is 0.2 m.