As the underground mining depth increasing gradually, in order to maintain the stability of the mining and mining, deep thick coal seam working face of strata movement rule and floor strata damage depth under large mining depth condition need to be studied. 2225 working face of Xingdong Mine was taken as example, its mining depth exceeds 1 000 m, in the recovery of working face, mining pressure observation to roadway surrounding rock was conducted, based on the mining pressure result, the length of working face affects strata movement rule and damage depth of floor strata, damage depth of floor strata achieved 45 m or so.