Abstract Gas overruns and explosions often occur in coal mining. To deal with this problem, the spatial structure model of a new non-ventilation excavation system is constructed. Combined with the model, a simulation experiment is conducted and the variations in gas concentration in each area of the system with variations in the amount of gas emission, drainage, and nitrogen curtain outlet velocity are obtained. The effectiveness of the gas barrier by the combined action of the gas drainage and nitrogen curtain is verified. This study provides the experimental basis for solving the problem of gas overruns and explosions, and is of great significance for realizing safe, efficient, and rapid excavation.