Abstract: In order to address the shortcomings of the "U+L" type comprehensive ventilation system used in coal mines, which relies on empirical design and lacks rationality, and has low ventilation efficiency and economy. On the basis of establishing comprehensive evaluation indicators for underground ventilation systems, a "U+L" type comprehensive ventilation system was established using 3D modeling software. Through theoretical analysis and numerical simulation analysis, the distribution of underground air volume and oxidation zone in different areas of the connecting roadway was analyzed from the perspectives of underground gas concentration control, coal spontaneous combustion prevention in goaf, ventilation economy, and management convenience. Through analysis, it was found that when the limit value of gas concentration at the upper corner of the underground is 1% and the maximum width of the oxidation zone in the goaf is 45m as the control standard, if the air flow demand of the working face does not exceed 1000 m³/min, the distribution distance of the connecting roadway cannot exceed 12 m; If the air volume requirement of the working face does not exceed 2000 m³/min, the distribution distance of the connecting roadway cannot exceed 36 m, laying the foundation for optimizing the underground ventilation system structure and improving ventilation safety.