When a gold mine uses upward fan-shaped medium long hole blasting and caving method,the too many powdered ores are produced and the brow line and back row borehole are seriously damaged.Therefore,based on theoretical analysis and field practice,the method to determine reserved maximum charge-free length in the hole with virtual blast hole bottom space is proposed,2 hole spaced charging plans with reserved length are devised,and field industrial tests are carried out.Industrial tests show that the hole spaced charging plan No.2 can effectively solve the blasting problems in the field,reducing hole blasting explosive amount,mitigating the impact of hole blasting vibration and obtaining significant technical and economic index.Empirical formula is summarized,providing new basis for the determination of reserved maximum charge-free length in hole.