Based on the characteristic of large primary bestraddle distance，long periodic fracture hanging roof and serious threaten to mine safety in hard roof long working face，three control caving methods of the primary fracture and the reasonable hanging roof length of periodic fracture are studied systematically. Three caving methods controlled by blast such as cycle shallow kerve，middle kerve and tip kerve are used to shorten the primary fracture distance of hard roof working face，of which the kerve depth and blasting quantities are analyzed and contrasted by establishing mechanical model of rock embedded beam at both ends. The results show that side kerve is the least，middle kerve is followed and cycle shallow kerve is the largest on the part of blasting quantities. By establishing and analyzing the model of cantilever rock beam，the reasonable overhanging length and face support strength are ascertained on the basis of designed resistance of face support. Additionally，the relation between overlying strata load and the working face controlling roof distance is deduced. This study has a successful application to working face 15102 of Qiling mine in Jincheng；and it can provide theoretical support and application guidance to control caving in hard roof under the corresponding conditions.