Abstract: The coking industry is an important VOCs emission source in China. Due to the complex production process, the VOCs emission characterization is lack, so a typical mechanized coking plant was selected to study. Samples were collected from coke oven chimney, coke pushing, coal charging and coke oven top. GC/MS was used to analyze the samples, and maximum increment reactivity (MIR) was used to quantify the ozone formation potential (OFP). The results show that:(1) The VOCs emitted from the coking plant mainly include alkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons and oxygenated VOCs, and more than 90 species. (2) The concentrations of the total volatile organic compounds generated from coking processes are significantly different. ρ(VOCs) from coke oven chimneys have the largest emissions (87.1 mg/m³), followed by coke pushing (4.0 mg/m³), coal charging (3.3 mg/m³) and coke oven tops (1.1 mg/m³). (3) The VOCs species in different coking processes are different, but mainly alkane and olefins. The coke oven chimney emits the most olefins, accounting for up to 66%, while the VOCs of the coal charging and coke pushing are dominated by alkanes (42% and 36% respectively), and the alkane and olefins emitted from coke oven top are similar (accounting for 31% and 29%). (4) Based on emission characteristics and maximum incremental reactivity studies, coke oven chimneys are the key link in the reduction of VOCs in the coking plants. Olefin is a key emission reduction species, especially ethylene, propylene, butene and 1, 3-butadiene. In addition, acetaldehyde, benzene, toluene cannot be ignored. The study uses ethane/propane/ethylene characteristic ratio as an indicator to distinguish VOCs emissions from different stages such as coke oven chimney, coke pushing, coal charging and coke oven top, which are of great significance for accurate traceability of VOCs.