The invention discloses a dampproof easily-absorbed magnetized slow-release fertilizer and a preparation method thereof. The dampproof easily-absorbed magnetized slow-release fertilizer is prepared from, by weight, 45-65 parts of soybean oil sediments, 35-40 parts of peat soil, 160-190 parts of sesame meal, 10-12 parts of magnesium nitrate, 26-28 parts of potassium hydrogen phosphate, 250-280 parts of Chinese medicine residues, 23-25 parts of EDTA chelate boron, 80-100 parts of flyash, 55-60 parts of iron pyrite ash, 30-35 parts of cassava starch, 5-8 parts of lime acetate, 20-24 parts of a composite bacterial strain and a proper amount of water. According to the fertilizer, raw materials contain sufficient nitrogen, phosphorus and potassium which are greatly needed by plants, meanwhile the EDTA chelate boron and chelating liquid of a coated layer are utilized, it is beneficial for the plants to absorb various microelements, fermented granulation of the soybean oil sediments, the peat soil and the like serve as organic matter and an anti-blushing agent, dryness and stabilization of fertilizer particles can be guaranteed to the maximum degree, the service life of the fertilizer is prolonged, and effectiveness of fertilizer nutrients is maintained.