Abstract: The mechanized mining of deep phosphate rock is affected by the conditions such as the in⁃ crease of ground stress and the fragmentation of rock mass. The exposed span of the stope can easily induce disasters such as roof caving and pillar instability. Reasonable optimization of the structural parameters of the stope is the key to ensure safe and efficient mining. Taking a deep phosphate mine in Guizhou as the en⁃ gineering background，aiming at the cutting and subsequent filling mining technology of cantilever road⁃ header，the field geological investigation，multi-method rock mass quality evaluation，Mathews stability chart method and FLAC3D numerical simulation were used to carry out the optimization of stope parameters. Through RMR，IRMR and MRMR classification methods，the quality of ore and rock is determined. The roof dolomite and phosphate rock are grade III medium rock mass，and the floor siliceous rock is grade II~III medium-good rock mass. Based on Mathews theory，the stability zoning threshold of the stope is cal⁃ culated，and the critical hydraulic radii of the stable zone and the unsupported transition zone are 5.30 m and 8.70 m，respectively. The length of the fixed stope is 50 m，and a total of 6 span conditions of 10~15 m are set for numerical simulation comparison. The evolution laws of surrounding rock stress，roof displace⁃ ment and deformation are analyzed. It is found that the disturbance of the 14 m span stope is the most signifi⁃ cant，and the stability of the 15 m span is slightly rebounded but the safety reserve is insufficient. The opti⁃ mal stope structure parameters obtained by comprehensive optimization are 50 m in length and 10 m in span.Under these parameters，the stress concentration of the stope is weak and the roof deformation is the small⁃ est. The field industrial test verifies that the optimized parameters can effectively inhibit the shear failure of surrounding rock and roof caving，and the overall stability of surrounding rock is good，which can provide reference for the design of mechanized mining parameters of similar deep phosphate mines.

Key words: deep phosphate mine, stope structure parameters, mathews chart method, numerical sim? ulation, stability of surrounding rock