The invention discloses a disease prevention and frost resistance fruit selenium-enriching nutritional agent for fruit trees and a preparation method of the disease prevention and frost resistance fruit selenium-enriching nutritional agent. The nutritional agent consists of the following components in part by weight: 20-40 parts of urea, 5-20 parts of ammonium dihydrogen phosphate, 35-65 parts of potassium dihydrogen phosphate, 15-35 parts of a boron fertilizer, 7-15 parts of a selenium fertilizer, 3-8 parts of salicylic acid, 1-3 parts of captopril, 4-10 parts of humic acid, 3-5 parts of pyrazinamide, 2-6 parts of metronidazole, 10-20 parts of paclobutrazol, 0.4-1 part of methylglutarate and 0.5-2 parts of disopyramide phosphate. The selenium-enriching nutritional agent disclosed by the invention has strong pertinence, can be used for solving multiple prominent problems existing in the planting of the fruit trees simultaneously, and has multiple effects such as disease prevention, rotten fruit prevention, frost resistance, dehiscent fruit prevention, fruit dropping prevention, fruit plumpness promotion, nutrition, selenium enrichment and the like.