Abstract: In order to study the safety stagger of lower coal mining roadway in close distance coal seam combined mining, taking No.3 and No.6 coal seam in a coal mine as the research background, this paper discusses the reasonable stagger of 6303 belt gateway and 3305 track gateway, establishes the rock mass damage model between layers affected by mining in No.3 coal seam working face, analyzes the damage state of mining floor in No.3 coal seam, and calculates the critical stagger of lower coal mining roadway. The research results show that the maximum yield failure depth of floor caused by fully mechanized mining in upper No.3 coal seam is 5.42 m, and the yield failure length around goaf is 4.79 m along the horizontal direction. The critical offset of roadway layout in the lower No.6 coal seam is 7.41 m. Combining with engineering analogy, the horizontal offset of 6303 belt gateway and 3305 track gateway is finally determined to be 10.0 m.