A WRF-CMAQ modeling system was used to simulate a haze event in Zhongshan during February 2015. Contributions from regional transport and local emissions to PM_2.5 concentrations as well as the emission reduction strategies were accessed by the model for a representative air pollution episode (Feb. ¹¹th to ¹²th, 2015). The simulations show reasonable agreement with the observations. The haze event was mainly affected by the intrusion of a weak cold front. The contribution percentage of emissions from Guangzhou and Foshan (GF), Zhongshan local, and emissions outside Guangdong Province were 33%, 30% and 27%, respectively. The contributions from non-local emissions were important in this haze event. The simulations also showed that local industrial and agricultural emissions contributed 13% and 8% of PM_2.5 in Zhongshan, while those two emissions in GF contributed 20% and 7%. After 30%, 50% and 70% reduction of agricultural emissions in Zhongshan and GF, PM_2.5 concentrations in Zhongshan deceased by 6%, 10% and 15%, and by 11%, 18% and 23% after the same reduction of industrial emissions in Zhongshan and GF. The emission reduction benefits showed little change under different strategies of agricultural and industrial reduction. Additionally, the emission reduction actions must be taken before the haze event, and it was most effective during the heavy polluted episode. However, the emission reduction became less effective when the haze event was ending.