To deeply analyze the emission characteristics of non-methane volatile organic compounds (NMVOC) from chemical industry in typical city, an emission inventory of chemical industry NMVOC in Nanjing was developed using the emission factor method based on detailed enterprise information from plant-by-plant onsite survey. The ozone formation potentials (OFPs) were calculated to assess the roles of NMVOC emissions in atmospheric oxidation. The uncertainty of this emission inventory was evaluated by using the Monte Carlo method. The plant-based emission inventory was compared with that based on energy and industrial statistics. The NMVOC emissions were estimated at 112000 metric tons for chemical industry in Nanjing at 2011. Oil refinery, basic chemical material manufacturing synthetic chemical industry, fine chemical industry, coke making and other chemical industry contributed 51.5%, 13.3%, 12.0%, 11.4%, 8.0% and 3.8%, respectively. The alkenes contributed more than 58 % to the total OFP. The uncertainty of this emission inventory was estimated to be (-74, +267%), in a form of 95% confidence interval. It was found that the VOC emissions based on statistics were underestimated by 18.8 % because of the omission of some emission sources in basic chemical material manufacturing and synthetic chemical industry. Besides, the spatial allocation of emissions according to population density failed to capture the emissions from the key emission sources. The comparisons between the two inventories demonstrated the importance of conducting detailed survey on improvement of emission inventory at city scale.