Abstract: Nanfen open-cut as mining the increase of depth economic benefits and the stability safety of its side slope that directly affects open-cut later production in advance split demolition is the effective measure of inprovement side slope stability one.this paper go on through introduction south fragrance open-cut ninteen the big diameter of Ø250mm and the especially big diameter of Ø310mm in advance application and the experiment of split demolition,have explained big diameter and especially big diameter in advance split demolition is fassible,for other open-cut mountain and similar project in advance split demolition is have certain reference value.