In order to study the mining law of multi-group coal seams, the corresponding numerical calculation of different working face lengths is carried out by means of UDEC numerical software. The analysis results show that the top goaf often has faster rock block migration speed and larger vertical displacement YDISP. The middle goaf is easy to appear large void zone, and the bottom goaf is easy to compaction. The stress concentration zone gradually transfers to both ends of the goaf, while the pressure relief zone appears in the top goaf ; with the increase of the inclined length of the top working face, the pressure relief range is larger.