Tropospheric ozone (O 3 ) has replaced PM 2.5 or PM 10 as the premier pollution in the North China Plain (NCP) during summer in recent years. A comprehensive understanding of the O 3 production in responding to the reduction of precursor emission over NCP is demanded urgently for the effective control policy design. In this study, the air quality modeling system RAMS-CMAQ (regional atmospheric modeling system-community multiscale air quality), coupled with the ISAM (integrated source apportionment method) module is applied to investigate the O 3 regional transport and source contribution features during a heavy O 3 pollution episode in June 2015 over NCP. The results show that the emission sources in Shandong and Hebei were the major contributors to O 3 production in the NCP. Not only more than 50 % O 3 mass burden in local regions, but also about 20–30 % and 25–40 % O 3 mass burdens in Beijing and Tianjin were contributed by the emission sources in these two provinces, respectively. On the other hand, the urban areas and most O 3 pollution regions of NCP were mainly dominated by the VOC-sensitive conditions, while "both control" and NO x -sensitive conditions dominated the suburban and remote areas, respectively. Then, based on the sensitivity tests, the effects of several hypothetical scenarios of emission control on reducing the O 3 pollution were compared and discussed. The results indicated that the emission control of industry and residential sectors was the most efficient way if the emission reduction percentage was higher than 40 %. However, when the emission reduction percentage dropped below 30 %, the power plant sector could make significant contributions to the decrease in O 3 . The control strategies should be promptly adjusted based on the emission reduction, and the modeling system can provide valuable information for precisely choosing the emission sector combination to achieve better efficiency.