The present invention relates to a pesticide solid nanodispersion and its preparation method. The said pesticide solid nanodispersion is composed of 0.001-90 parts by weight of pesticide, 0.001-50 parts by weight of surfactants and 5-99.9 parts by weight of water-soluble carriers. The said pesticide is one or more pesticide(s) selected from poorly water-soluble insecticides, fungicides, herbicides or plant growth regulators; the particle size of the said solid nanodispersion is less than 1µm. Compared with the prior art, the pesticide of the present invention has smaller particle size, more uniform dispersibility and better coating effect of surfactants. The content of surfactants may be less than 1%, even less than 0.1%, and can maintain good dispersibility and stability as well. The method of the present invention can eliminate the usage of the organic solvent and significantly save production cost. It not only can decrease the usage of pesticides by the way of improving the effective utilization, but also can significantly reduce residues of the pesticide, harmful solvents and additives in the agricultural products and environmental pollution, to ensure security of grain, food and ecology.