Abstract: Under the conditions of U-type ventilation，the numerical simulation on the characteristics of flow field，the distribution of methane density and the rule of air density change are studied by numerical simulation software of CFD at the mining face spaces.The simulations show that from intake airflow into roadway，working face and to return airway，the characteristics of airflow field shows to be simple firstly，complex next and simple again.The flow field is the most complex at the crossing of the intake airflow roadway and the return airway; The gas concentration at working face space shows gradually increasing along the airflow direction with larger variety only appearing at local position，and gas concentration along coal wall is higher than that along mining-out area; Under the condition of U-type ventilation，gas can be easily accumulated to be the highest level around the top of intake airflow roadway close to coal wall and the upper corner，and the gas concentration at the upper corner is triangle in shape.

Key words: U-type ventilation, CFD, Flow field characteristics, Methane distribution characteristics