With respect to three vents located on both sides of the fire source in an asymmetrical arrangement, series of CFD simulations and reducedscale experimental tests are carried out. And further analysis is undertaken for several parameters, such as airflow distribution, flue gas temperature and smoke horizontal diffusion distance etc, with different combinations of the longitudinal velocity and exhaust rate. It is found that horizontal diffusion distance of smoke is confined in three vents bordering the fire source and optimization design with minimal exhaust rate is further proposed. With multiple CFD simulations, series of dimensionless correlations are recommended for further tunnel fire safety design with some parameters, such as heat release rate, tunnel inclination and optimized parameters with slope variation.