Based on the ozone mass concentration data in Ningxia from 2015 to 2018, the variations of O3 mass concentration in five cities of Ningxia were analyzed and compared, and the influences of airflow on O3 mass concentration in five cities of Ningxia were discussed by using back trajectory cluster analysis method and the global data assimilation system. The results show that the 90% quantile of O3 mass concentration in Shizuishan was the highest (159 μg·m-3), followed by Yinchuan (154 μg·m-3), Zhongwei (149 μg·m-3), Wuzhong (137 μg·m-3), and Guyuan (132 μg·m-3) during 2015-2018. In the past four years, the O3 mass concentration in Shizuishan decreased slightly, while that in other four cities increased. The days on which primary pollutants was O3 was 124 days in Shizuishan, 119 days in Zhongwei and 103 days in Yinchuan. The days on which primary pollutants was O3 and air quality was good and light pollution increased in all 5 cities. Except for Guyuan, the frequency of O3 pullution processes with 6 d and 7 d duration increased in other cities, especially in Yinchuan and Zhongwei. For Shizuishan, Yinchuan and Wuzhong, the middle-distance and short-distance northwest airflow accounted for the highest percentage of the total airflow trajectory, followed by the southeast airflow and the north airflow. For Zhongwei and Guyuan,the percentage of the southeast airflow was the highest, followed by the short-distance northwest airflow, and then the middle-distance and long-distance northwest airflow. The northern airflow from central Mongolia, central and western Inner Mongolia, across the northern and central Ningxia was the most important transport path affecting the O3 mass concentration, while the southeastern airflow from south central Shaanxi, northeastern Gansu and middle east Ningxia was the most important transport path affecting the ozone mass concentration in Shizuishan, Yinchuan, Wuzhong and Zhongwei.