Abstract: Humic acid water-soluble fertilizer contains active nitrogen, phosphorus, potassium complex nutrition, as well as boron,zinc, copper and other elements, nutrition uniformity, not only can promote crop metabolism, accelerate cell division, strengthen physiological and biochemical activities, but also have synergistic nutrition, widely used in agriculture. In the process of detecting molybdenum content in water-soluble fertilizer by Determination of Copper, Iron, Manganese, Zinc, Boron and Molybdenum Content（NY/T 1974-2010）, the pretreatment process was not satisfactory. Based on this, the pretreatment technology of NY/T 1974-2010 for determination of molybdenum element content in humic acid water-soluble fertilizer was improved. The samples were incinerated at high temperature, dissolved in acid, filtered and analyzed with filtrate. The sintering conditions were optimized with Ehrlicard reagent, and the average recovery rate was 105%. It has been proved that the test data are accurate and reliable, and the interference of sample base is effectively eliminated.