A preparation method of a fertilizer special for kidney bean comprises the following steps: raw materials metering, mixing, raw material melting, liquid material slurry filtration, slurry spraying, cooling and granulation, granule screening, and finished product packaging, the fertilizer comprises the following components and raw materials: 18-20 parts of urea, 4-5 parts of monoammonium phosphate, 18-20 parts of potassium chloride, 3-4 parts of calcium oxide, 2-4 parts of zinc sulfate and 4-6 parts of boron fertilizer. The special fertilizer prepared by the method is uniform in release of fertilizer efficiency, is relatively long in effect time, is convenient to apply, is not easy to scatter, and is less in loss, by applying the fertilizer, kidney bean plants are vigorous in growth vigour, the plant height is 2 m, the stem diameter is 0.8 cm, the blossom and podding time is long, the yield is high, the net weight of yield per mu is 2000kg, the product fruit is dark green in color, the product fruit beanpod is smooth, long and thin, good in commercial appearance, easy to sale, and capable of achieving better economic benefit.