To investigate the formation mechanism of heavy haze in fall and winter season of Zhengzhou, online measurements of hourly concentrations of elements in PM_2.5 using the ambient metals analyzer and meteorological instrument were conducted from Nov. 21^th to 29^that an urban site of Zhengzhou University. Results show that the concentrations of As, Mn, Fe, Cu, and Zn in Zhengzhou during the sampling periods were higher than in other cities. The polluted air mass transported from northeastern regions of Zhengzhou, and the lower wind speed, higher relative humidity and calm conditions which accumulating local pollutant emissions, based on the statistical analysis of meteorological data, were the major meteorological parameters causing the two heavy haze episodes. Meanwhile, quantitative source apportionment from the positive matrix factorization (PMF) model showed that dust, vehicle, industrial emission and combustion were the major sources of elements in PM_2.5, which accounting for 36.8%, 27.6%, 21.0% and 14.6%, respectively. The contribution of dust source in cleaning day was relatively higher and that of motor vehicle and combustion source increased significantly during heavy haze period.