Abstract: To accurately determine the moving angle of the surface road affecting the iron mine in He⁃ bei Province，based on the critical granular column theory，the engineering analogy method and theoretical analysis method were used to optimize the study of the rock moving angle affected by the surface road of this iron mine，and the PFC2D numerical simulation was adopted for verification. The results show that by using the critical granular column theory，the calculated rock moving angle increased from 65° to 71°，and the rock moving angle obtained by the numerical simulation method was approximately 73°. This indicates that the rock moving angle calculated by the critical granular column theory is relatively reliable. Therefore，the critical granular column can provide certain lateral supporting force for the collapse pit side wall under the caving mining conditions，and the optimized 71° rock moving angle is more in line with the actual engineering situation of this mine compared to the original design of 65°. After re-determining the road protection range based on the 71° rock moving angle，when mining reaches the -320 m level，approximately 1.75 million tons of overburden resources under the road can be released，providing a technical basis for extending the ser⁃ vice life of the mine，and being of great significance for the continued production of the mine.

Key words: caving method, critical granular column, rock movement angle