The invention discloses a coast salinized soil improvement method improving plough layer soil nitrogen immobilization capability; the method comprises the following steps: laying subsurface pipes, washing, ploughing soil, pre-applying soil composition conditioning agent, applying organic-inorganic composite fertilizer, supplementing bacterium source, and dry spreading a soil amendment in a fallow period. The coast salinized soil is large in salt content, high in soil hardening level, and severe in nitrogen nutrient loss in leaching; the novel method considers these problems, organically couples soil improving physical, chemical and biological means, thus developing the coast salinized soil improvement technology and application method thereof that improves salinized soil nitrogen immobilization capability and salinized soil physical and chemical properties; subsurface pipe drainage and organic-inorganic composite fertilizer are combined; soil composition conditioning agent and soil amendment are respectively applied before cultivation and in the fallow period; microbe inocula is supplemented after base fertilizer and additional fertilizer, thus greatly improving plough layer salinized soil nitrogen immobilization capability, and improving salinized soil physical and chemical properties.