An ion migration tube, comprising an interior space and an ion gate disposed within the interior space and configured to be opened or closed, the interior space comprising an ionization region having an absolute value of potential V1 and a migration region isolated from the ionization region by the ion gate, so that matters which enters the ion migration tube from one end of the ionization region, are ionized within the ionization region and then are driven by an electric field to enter the migration region; wherein, the ion gate disposed between the ionization region and the migration region comprises a first ion gate grid having an absolute value of potential V2 and a second ion gate grid having an absolute value of potential V3, the first ion gate grid and the second ion gate grid are parallel to each other and spaced apart from each other by an insulation sheet so as to divide the ion migration tube into the ionization region and the migration region; the migration region comprises at least a first migration region electrode having an absolute value of potential V4 and a second migration region electrode having an absolute value of potential V5, and the second migration region electrode is farther from the second ion gate grid than the first migration region electrode; and wherein the ion migration tube is configured such that, upon the ion gate being opened, a potential well is formed between the first ion gate grid and the first migration region electrode for ionized ions so as to compress an ion group entering the migration region, characterized in that the ion migration tube is configured such that, upon the ion gate being opened, the absolute value of potential V2 of the first ion gate grid is larger than the absolute value of potential V4 of the first migration region electrode, the absolute value of potential V4 of the first migration region electrode is larger than the absolute value of potential V3 of the second ion gate grid, and the absolute value of potential V3 of the second ion gate grid is larger than or equal to the absolute value of potential V5 of the second migration region electrode; or the ion migration tube is configured such that, upon the ion gate being kept closed, the absolute value of potential V1 of the ionization region is larger than or equal to the absolute value of potential V3 of the second ion gate grid, the absolute value of potential V3 of the second ion gate grid is larger than the absolute value of potential V2 of the first ion gate grid, the absolute value of potential V2 of the first ion gate grid is larger than the absolute value of potential V4 of the first migration region electrode, and the absolute value of potential V4 of the first migration region electrode larger than the absolute value of potential V5 of the second migration region electrode. wherein, the ion gate disposed between the ionization region and the migration region comprises a first ion gate grid having an absolute value of potential V2 and a second ion gate grid having an absolute value of potential V3, the first ion gate grid and the second ion gate grid are parallel to each other and spaced apart from each other by an insulation sheet so as to divide the ion migration tube into the ionization region and the migration region; the migration region comprises at least a first migration region electrode having an absolute value of potential V4 and a second migration region electrode having an absolute value of potential V5, and the second migration region electrode is farther from the second ion gate grid than the first migration region electrode; and wherein the ion migration tube is configured such that, upon the ion gate being opened, a potential well is formed between the first ion gate grid and the first migration region electrode for ionized ions so as to compress an ion group entering the migration region, characterized in that the ion migration tube is configured such that, upon the ion gate being opened, the absolute value of potential V2 of the first ion gate grid is larger than the absolute value of potential V4 of the first migration region electrode, the absolute value of potential V4 of the first migration region electrode is larger than the absolute value of potential V3 of the second ion gate grid, and the absolute value of potential V3 of the second ion gate grid is larger than or equal to the absolute value of potential V5 of the second migration region electrode; or the ion migration tube is configured such that, upon the ion gate being kept closed, the absolute value of potential V1 of the ionization region is larger than or equal to the absolute value of potential V3 of the second ion gate grid, the absolute value of potential V3 of the second ion gate grid is larger than the absolute value of potential V2 of the first ion gate grid, the absolute value of potential V2 of the first ion gate grid is larger than the absolute value of potential V4 of the first migration region electrode, and the absolute value of potential V4 of the first migration region electrode larger than the absolute value of potential V5 of the second migration region electrode.