NOVELTY - Moisture-resistant synergistic additive comprises lignin, composite deodorant, rice bran, soybean meal, polyacrylamide, papermaking black liquid, biogas fermentation residue, fly ash, hydroquinone, urease inhibitor phenyl phosphorodiamidate, calcium silicon powder, lignite, sawdust and effective microorganism solution. The composite deodorant comprises Ligusticum chuanxiong, Baeckea frutescens, Eucalyptus fruit, plantain, zeolite powder, straw biomass charcoal, sodium pyrophosphate, chitosan, sodium citrate, peach gum powder and zinc chloride.    USE - The moisture-resistant synergistic additive is useful for preparing fertilizer.    ADVANTAGE - The synergistic additive has excellent moisture resistance, and can reduce diffusion rate of nutrients in soil.    DETAILED DESCRIPTION - Moisture-resistant synergistic additive comprises 1-2 pts. wt. lignin, 3-6 pts. wt. composite deodorant, 2-4 pts. wt. rice bran, 3-5 pts. wt. soybean meal, 1-3 pts. wt. polyacrylamide, 2-4 pts. wt. papermaking black liquid, 0.2-0.4 pt. wt. biogas fermentation residue, 3-5 pts. wt. fly ash, 0.3-0.5 pt. wt. hydroquinone, 0.4-0.8 pt. wt. urease inhibitor phenyl phosphorodiamidate, 3-5 pts. wt. calcium silicon powder, 3-6 pts. wt. lignite, 3-5 pts. wt. sawdust and 1-3 pts. wt. effective microorganism solution. The composite deodorant comprises 2-4 pts. wt. Ligusticum chuanxiong, 1-3 pts. wt. Baeckea frutescens, 1-3 pts. wt. Eucalyptus fruit, 2-4 pts. wt. plantain, 3-5 pts. wt. zeolite powder, 1-3 pts. wt. straw biomass charcoal, 0.1-0.3 pt. wt. sodium pyrophosphate, 1-2 pts. wt. chitosan, 0.1-0.3 pt. wt. sodium citrate, 2-3 pts. wt. peach gum powder and 0.3-0.4 pt. wt. zinc chloride, and is prepared by drying Ligusticum chuanxiong, Baeckea frutescens, Eucalyptus fruit and plantain, crushing, sieving through 100-200 mesh sieve to obtain medicine powder, uniformly mixing zeolite powder and straw biomass charcoal, processing under UV radiation for 18-22 hours, adding medicine powder and peach gum powder, mixing to obtain composite powder, adding water to remaining materials, mixing and then uniformly spraying on composite powder and drying.