An ion guiding device (3) and method, the ion guiding device (3) having: a group of electrode arrays distributed along an axis in space, and a power supply providing an asymmetric alternating current (AC) electric field substantially along the axis; the AC field asymmetrically alternates between positive and negative along the axis to drive the ions move in the direction corresponding to said AC electric field such that ions are guided into said ion guiding device (3) in a continuous or quasi-continuous flow manner while being guided out in a pulsed manner along the axis.