Abstract: Improving the filling and roof contact effect of mining chamber first-step is of great signifi⁃ cance for ensuring the safe mining of the second-step mining chamber. In response to the problems such as large size of the void area in the high-stage large-diameter deep-hole mining area of Zhongguan Iron Mine and poor filling and roof contact effect，a filling slurry flow model of the mining area was constructed. Com⁃ bined with production practice，the settlement mechanism of the filling slurry in the void area was ana⁃ lyzed. It was found that when a single point was discharged and the filling slurry flowed over a long dis⁃ tance，in the void area，it often accumulated into a filling slope centered on the discharge port，with a higher middle part and lower periphery. Based on this，a secondary roof contacted technology scheme of segmented filling+"filling+grouting" was proposed. One is to optimize the single-point discharge to multi⁃ ple-point discharge; the other is to divide the top void area of the mining chamber into two sections for fill⁃ ing，reducing the void area between the filling body and the roof caused by uneven slurry flow. Finally，the "filling + grouting" method was adopted to conduct pressure grouting to fill the un-contacted void area. Through engineering practice，the optimized filling and roof contacted scheme has shown good results， with a roof contacted rate of over 92%，and can be further promoted and applied.

Key words: large diameter deep-hole, first-step mining chamber, stage filling, grouting to fill the gap, roof contact optimization