The invention discloses a preparation method of modified micron zero-valent iron and an application method of the modified micron zero-valent iron in remediation of heavy 
metal contaminated soil. The preparation method of the modified micron zero-valent iron comprises the steps of cleaning of iron raw materials, preparation of micro iron, ultrafine 
grinding and modifying treatment. A modifying agent composed of water, 
xanthan gum, 
sulfide, a stabilizing agent, 
zeolite and 
blast furnace slag is adopted in the step of modifying treatment. The preparation method of the modified micron zero-valent iron has the beneficial effects that the production process of the modified micron zero-valent iron is simple, and the effect similar or superior to micron zero-valent iron is achieved while the cost is reduced; and in addition, the reaction activity is controlled, the 
oxidation rate is decreased, excellent stability is obtained, and the acting time of the micron zero-valent iron is longer. By the adoption of the application method of the modified micron zero-valent iron, the remediation cost of heavy 
metal contaminated underground water is further reduced. According to the preparation method of the modified micron zero-valent iron and the application method of the modified micron zero-valent iron in remediation of heavy 
metal contaminated soil, 
organic fertilizer is added in the 
soil treatment process so that the 
fertility of soil can be improved, the structure of soil can be improved through 
humic acid produced by the 
organic fertilizer, heavy metal elements, such as lead, 
chromium and 
arsenic, in underground water can be removed, and the concentration of pollutants such as 
nitrate and 
perchlorate can be reduced.