The authors generalized the ground pressure problems occured in the process of mining No. 91 orebody in Tongkeng Tin Mine,and pointed out the characteristic of ground pressure activity,the filling sequence of mined-out areas,the mining sequence of the ore pillars and the miniforing and controlling measures of the ground pressure which should be adepted during mining No.91 orebody.These are of great importance to the safety mining of ore-pillars and the increase of economical benefits of the mine.