Abstract: To reduce the deliveries of free radicals in mainstream cigarette smoke, 15 cigarette samples of different auxiliary material parameters, including cigarette paper permeability, filter ventilation rate and pressure drop of filter rod, were prepared with single factor design method, and the deliveries of free radicals in mainstream smoke of the samples were determined. The results showed that:1) When cigarette paper permeability increased from 20 to 80 CU, the deliveries of gas phase free radicals increased from 6.87×10¹⁴ to 9.30×10¹⁴ spins per cig., while the deliveries of solid phase free radicals decreased from 1.10×10¹⁴ to 0.75×10¹⁴ spins per cig., their change rates were 35.37% and - 31.82%, respectively. 2) As filter ventilation rates increased from 0 to 50%, the deliveries of gas phase free radicals increased from 6.52×10¹⁴ to 1.16×10¹⁴ spins per cig., at the same time, the deliveries of solid phase free radicals decreased from 1.09×10¹⁴ to 0.48×10¹⁴ spins per cig., their reduction rates were 82.21% and 55.96%, respectively. 3) When the pressure drop of filter rod increased from 3400 to 5000 Pa, the deliveries of gas phase free radicals increased from 8.16×10¹⁴ to 5.21×10¹⁴ spins per cig., meantime, the deliveries of solid phase free radicals decreased from 1.03×10¹⁴ to 0.73×10¹⁴ spins per cig., their reduction rates were 36.15% and 27.72%, respectively. Therefore, it is impossible to reduce the deliveries of free radicals in cigarette smoke by increasing cigarette paper permeability. However, the deliveries of gas and solid phase free radicals in cigarette smoke could be obviously decreased with the increase of filter ventilation rate and pressure drop of filter rod.