The invention discloses a nano organic fertilizer and a preparation method of the nano organic fertilizer. The nano organic fertilizer is prepared from the following ingredients through fermentation in parts by weight: 70-120 parts of corn flour, 75-90 parts of a compound microorganism bacterium agent, 40-50 parts of water, 10-15 parts of nano CaCO3, 10-15 parts of nano TiO2, 4-10 parts of nanocarbon, 12-20 parts of soybean meal, 9-15 parts of peanut bran, 14-18 parts of spent mushroom compost, and 22-29 parts of coffee grounds. The nano organic fertilizer is low in cost and is well absorbed,the air permeability of the soil is improved, a plant absorbs the nano organic fertilizer more easily, the utilization ratio is increased to 80-90%, the loss of the organic fertilizer is reduced, thegrowth and the development of the plant are also helped, the growth and the development of flowers and fruits of the plant are promoted, the soil is activated, the number of beneficial microorganismsis increased exponentially, the vitality is strengthened, and the yield of the crop is effectively increased.