The invention discloses a preparation for preventing and treating eriosoma lanigerum. The preparation is prepared from diesel oil, ethanol, soap powder and water in a weight ratio of 3:3:1:150. When the preparation is used, firstly, the diesel oil is dissolved in ethanol, the soap powder is dissolved in a small amount of water, and then, the two mixed liquids are added into water and uniformly mixed to prepare the preparation for preventing and treating eriosoma lanigerum. The invention further discloses a method for preventing and treating eriosoma lanigerum. The preparation has a remarkable prevention effect, saves labor and time, has the advantages of low cost, simple preparation and convenience in use, and realizes safe, high-quality and high-performance apples. By adopting the preparation and the method, the control rate of eriosoma lanigerum can be greatly improved, the damage of eriosoma lanigerum to tree bodies and fruits can be avoided, the tree bodies can grow healthily, the yield and quality of apples can be promoted, the technology is low in cost, and the economic benefits of farmers can be increased finally.