Abstract: After the mining in the mine adopts the staged ore chamber backfilling method to form the collapse area，and before the tailings are cemented and filled，in order to solve the potential safety hazards such as roof collapse and pillar instability，firstly，the surrounding rock characteristics data are collected through the combination of digital close-range photography and manual measurement.Then，various meth⁃ ods such as Q system classification are used to evaluate the quality grade of the collapse area and its sur ⁃ rounding rock mass.Secondly，the stability of the pillars is analyzed and evaluated by using pillar stress calculation formulas，Bieniawski empirical formulas，etc.，and the roof stability risk is quantified by using Barton ultimate span analysis method and Mathews stability diagram method.Finally，based on the stabili⁃ ty analysis and evaluation results of the three sub-factors of pillar，roof span，and roof exposure area，the risk level of the collapse area is determined by the most unfavorable principle，and the safety control prin⁃ ciples of "strong mining，strong extraction，and strong filling"for the ore chamber mining and collapse ar⁃ ea treatment are adopted to ensure production safety.The research results show that in the Makeng Iron Mine，by applying the most unfavorable principle，when the rock mass quality grade is grade III and the most unfavorable rock mass is considered，the comprehensive determination of the safety risk level of the collapse area is as follows:when the mining length of the ore chamber is ≤48 m，the collapse area is of low risk.When it is 48 ~100 m，it is of general risk.After applying the safety control principles，the mining cy⁃ cle is shortened and the tailings cementation and roof backfilling to reinforce are carried out in time.In the application of the largest goaf volume of 67-7R-1 unit，after 6.5 months，the mine chamber is completely emptied，and through three-dimensional scanning analysis，the actual collapse volume of the goaf ac⁃ counts for 3.8%of the designed volume，achieving safe，stable，and efficient mining of Makeng Iron Mine.

Key words: goaf, risk quantitative classification, rock mass quality classification, Barton limit span analysis method, Mathews stability chart method