Emission factors of selected air pollutants being CO, CO2, SO2 and NO for coke quenching of the Coking Factory of Thai Nguyen Iron and Steel Joint Stock Company were studied. Concentrations of these pollutants were measured by a combustion gas analyzer, Quintox KM - 9106. Based on data monitored, functions on the correlations between the emission and the time during coke quenching were determined. Total emissions and emission factors of the pollutants for the process were determined. Emission factors obtained in this study are in the same range with those of other studies.