The present invention discloses a rectangular ion trap device and method for ion storage. The device comprises a front end cover including left electrode, middle layer insulator, and right electrode, wherein the left electrode and the right electrode are respectively positioned at both sides of the middle layer insulator; a rear end cover, wherein the rear end cover has the same axis as the front end cover, and the central position of the rear end cover electrode is penetrated; the front and rear electrodes and the upper and lower electrodes are symmetric along the axis of the front end cover, and these electrodes form a space region for ion storage about the axis between the front end cover and the rear end cover electrode. The present invention can increase the number of ions in storage within a unit time prominently.