The abnormalities in the mine ventilation system can reflect the risks and hidden dangers during the mine production. By combining the basic information of the mine and the ventilation monitoring data with the production status, the gas concentration and wind speed are used as the calculation indicators, and the k-nearest neighbor (KNN) is used to study the abnormal change characteristics of calculation indicators of mine ventilation system in different ventilation periods, and a ventilation hazard warning model was constructed and the model results were compared and validated. In addition, the dominant factors of the warning level were obtained by combining the grey correlation analysis (GCA). The results show that under different ventilation periods (easy ventilation period and difficult ventilation period), the correct rates of calculation and verification in easy ventilation period and difficult ventilation period are 95.65% and 97.82% respectively. It can be seen that the accuracy of the warning model is over 95%, which has good application and promotion value. Furthermore, the correlation coefficient of the wind speed in two periods is relatively high, which is indicating that the speed is the main indicator that affects the warning level. The research of this paper can provide theoretical support for realizing the intelligent management of mine risk in advance and short-term early warning.