Disclosed is an ion gate for a dual IMS and method. The ion gate includes an ion source, a first gate electrode placed on one side of the ion source, a second gate electrode placed on the other side of the ion source, a third gate electrode placed on the side of the first gate electrode away from the ion source, a fourth gate electrode placed on the side of the second gate electrode away from the ion source, wherein during the ion storage, the potential at the position on the tube axis of the ion gate corresponding to the first gate electrode is different from the potentials at the positions on the tube axis corresponding to the ion source and the third gate electrode, and the potential at the position on the tube axis corresponding to the second gate electrode is different from the potentials at the positions on the tube axis corresponding to the ion source and the fourth gate electrode. According to the present invention, after sample gas enters the ion gates, charge exchange with reaction ions occurs between the first gate electrode and the second electrode, and positive and negative ions are continuously stored into the storage regions for the positive and negative ions. This leads to an improvement of utility rate of ions. Then, the ions are educed in a step-wise manner from the storage regions for the positive and negative ions by a simple control of a combination of the electrodes.