The Weather Research and Forecasting model coupled with Chemistry (WRF/Chem) is used to simulate the stratospheric intrusion event occurring on 6 March 2013 and investigate the impact of stratospheric intrusion on the enhancement of ozone in the lower troposphere. An upper boundary condition scheme is employed in the simulations to overcome the problem that WRF/Chem does not have the capability to simulate O₃ formation in the stratosphere. A series of observational data including ozone sounding data, surface O₃, CO, NO, relative humidity, temperature, winds together with ECMWF (European Centre for Medium-Range Weather Forecasts) Interim data are used to evaluate the model results. The WRF/Chem shows reasonable performance on simulating the meteorological processes that control the stratospheric intrusion. Several findings are identified from the detailed analyses of the modeling results. First, the subtropical jet at high altitude was responsible for this stratospheric intrusion event. When Hong Kong was located at the left side of the entrance of the subtropical jet zone where subsidence was dominated, the ozone-enriched air was transported from the stratosphere to troposphere. Second, the stratospheric intrusion caused substantial enhancement of ozone in the lower troposphere over the Hong Kong region. For instance, the surface ozone increased by 21.3 ppb (1 ppb=1×10^-9) (nighttime) at Tap Mun station, Hong Kong. The analyses of surface observational data including winds and CO further confirmed the contribution of stratospheric intrusion to the increase in surface O₃. Third, the stratosphere-troposphere exchange fluxes of ozone calculated with a box model and the Wei formula are comparable to each other (-1.42×10^-3 kg m^-2 s^-1 versus -1.59×10^-3 kg m^-2 s^-1), and consistent with the findings of other studies. Furthermore, the results are comparable when the dynamic and thermodynamic tropopause heights are utilized in the flux calculations.