The present invention discloses a filter device. The filter device comprises a housing with an air inlet and an filtered air outlet; a high voltage electric field region provided between two ends of the housing, wherein the direction of the electric field is perpendicular to the direction along which the air is introduced into the housing; an ionization source provided in the electric field region to ionize the ionizable pollutants present in the air introduced from the air inlet and form the resultant ionized pollutants which will move towards both ends of the housing under the influence of the electric field; and a discharging device for discharging the ionized pollutants which have arrived at the ends of the housing out of the filter device. The present invention also relates to a filtering method of using the filter device, and a trace detector. The filter device can be used to ionize the ionizable interferents existed in the air, separate the ionized interferents from the other components of the air under the influence of the electric field, and discharge the interferent out of the filter device, thereby reducing the consumption of the consumables or even eliminating the need for consumables. The filter device in accordance with the present invention is applicable to a trace detector based on ion mobility technology for the detection of trace amounts of substances.