NOVELTY - Pesticide preparation involves using controlled releasing composite material, where pyraflufen-ethyl is dissolved in water in the weight (g) ratio of 1:1.5-1:9. Pyraflufen-ethyl is dispersed by using ultrasonic wave to obtain a suspension. Solution is added to infusorial earth particle in negative pressure by using freeze-drying method. Infusorial earth particle is disposed in the sealing container and then sealed at vacuum state. Suspension containing pyraflufen-ethyl is injected into the container, where pyraflufen-ethyl molecule is absorbed on the surface of infusorial earth particles.    USE - Method for preparing pesticide (claimed).    ADVANTAGE - The pesticide preparing method releases active ingredient slowly, and thus solves the problems of frequent medication, large doses, low medicine utilization ratio, side effect and pollution caused by loss of medicine.    DETAILED DESCRIPTION - Pesticide preparation involves using controlled releasing composite material, where pyraflufen-ethyl is dissolved in water in the weight (g) ratio of 1:1.5-1:9. Pyraflufen-ethyl is dispersed by using ultrasonic wave to obtain a suspension. Solution is added to infusorial earth particle in negative pressure by using freeze-drying method. Infusorial earth particle is disposed in the sealing container and then sealed at vacuum state. Suspension containing pyraflufen-ethyl is injected into the container, where pyraflufen-ethyl molecule is absorbed on the surface of infusorial earth particle to permeate into the hole due to negative pressure. The particles are frozen and dried after 1-10 minutes to obtain dosage form. Sodium alga acid/calcium salt is used to form natural high molecule gel that is used to cover the dosage form. Infusorial earth particle and sodium alga acid of the dosage form are selected in the weight (g) ratio of 1:2-1:4. Sodium alga acid is added to the water with stirring the mixture at room temperature to obtain sodium alga acid solution, where the mass concentration of sodium alga acid is 1-7 wt.%. Infusorial earth particle is dissolved and dispersed in water in the weight ratio of 1:1.5-1:9 by using ultrasonic wave to obtain the infusorial earth particle suspension. Sodium alga acid solution is mixed with infusorial earth particle suspension to obtain gel system. Gel system is dripped in calcium ion cross-linking gel particles by using an injector to prepare ion cross-linking gel particle of cross-linking agent. The particles are washed by using distilled water and then dried to obtain a pesticide.