The invention discloses an original soil improving method and device suitable for severe saline-alkali soil. Technical means such as an integrated engineering water permeability measure, sticky soil layer breaking, filter material backfilling and brackish water flood irrigation are adopted, so that salt on a plough layer of the saline-alkali soil is leached to a subsoil layer and is not returned,not only is the salt stopped from ascending along capillary tubes, but also a descending passage of a salt leaching water is formed, after the technical means is applied, the effect on leaching the salt in the soil at the depth of 0-60cm of the saline-alkali soil is obvious, the total salt of the soil in the plough layer is maintained at 6-9g/kg, and the total salt of the soil is leached to the depth lower than 80cm; and meanwhile, due to the utilization of a gravel layer with the depth of 60-70cm, the ascending of the salt can be effectively stopped, the salt on the subsoil layer can be prevented from upwards moving, the salt on the plough layer can be effectively controlled, the salt of the soil can be reduced by 50-60%, and the method and device have wide practicability for the technical field of saline-alkali soil improvement.