The invention discloses a longitudinal pockels cell employing ionic liquid as an electrode, and belongs to the field of high-power laser devices. The ionic liquid is adopted as the electrode of the longitudinal pockels cell; protective light windows are arranged on light-pass surfaces on two sides of electro-optical crystal of the longitudinal pockels cell, and are sealed with an outer light window to form an ionic liquid cavity; the ionic liquid in the ionic liquid cavity adopts a thin-layer state as the electrode, so that the longitudinal pockels effect is achieved. According to the longitudinal pockels cell employing the ionic liquid as the electrode, a high-voltage gas is not needed to discharge electricity to form a plasma electrode; the drive voltage of the longitudinal pockels cell is lower than that of the plasma electrode pockels cell; the system is simple in structure, large in caliber and low in cost; the ionic liquid electrode is free of damaging threshold limitation; the longitudinal pockels cell can be applied to Q modulation and inter-stage isolation of the laser device.