The invention relates to a polymerized coated fertilizer for reducing pest and disease damage of strawberries by utilizing modified bamboo fiber. The polymerized coated fertilizer is prepared from the following raw materials in parts by weight: 16-24 parts of ammonium sulfate, 1-2 parts of potassium-magnesium sulfate, 7-9 parts of ammonium bicarbonate, 22-28 parts of extruded soybeans, 0.2-0.4 part of enzyme microorganism, 26-29 parts of rapeseed cakes, 18-24 parts of brewer grain, 6-8 parts of molasses, 15-19 parts of potassium sulfate, 17-23 parts of phosphorus pentaoxide, 20-25 parts of dry duck manure, 12-14 parts of corn starch, 32-38 parts of dry rabbit manure, 6-9 parts of EM microbial agent, 11-13 parts of modified bamboo fiber, 2-4 parts of polyvinyl alcohol, 3-4 parts of diatomite, 2-3 parts of nanocarbon, 1-2 parts of zinc sulfate, 3-5 parts of itaconic acid, 1-2 parts of dimethyl tin oxide, 0.2-0.4 part of hydroxy-propyl acrylate, 0.6-1.2 parts of sorbitan monostearate, 0.1-0.3 part of ammonium supersulfate, and a proper amount of water. The fertilizer has water retention property, soil is loosened, the soil quality is improved, and the fertilizer has a good role in inhibiting bacteria.