Currently most of the aerosol chargers have poor penetration and charging efficiencies for 1 ～ 3 nm aerosols. A new soft X-ray aerosol charger is developed and evaluated. While maintaining similar intrinsic charging efficiency to the other chargers, its penetration efficiency is significantly increased through the improvement of the structure design. Laboratory evaluations show that, compared with commercialized TSI 3088 soft X-ray charger, the penetration efficiencies of the new developed charger for sub-3 nm aerosols have been increased by 175% ～ 300% and 115% ～ 173% under 1.0 and 2.5 L · min －1 flow rates, respectively. Meanwhile, the intrinsic charging efficiencies of the new charger for 10 ～ 40 nm and sub-3 nm aerosols is basically consistent with the intrinsic charging efficiencies estimated by a well-accepted Fuchs steady state approximation formula and those of the other similar aerosol chargers. Therefore, compared with the existing commercial chargers, the new developed charger is beneficial for its higher extrinsic charging efficiency for sub-3 nm aerosols, which indicates its potential application value.