The invention discloses a facultative anaerobic fermentation fungicide. The facultative anaerobic fermentation fungicide is prepared from facultative anaerobic fermentation flora. The facultative anaerobic fermentation flora is prepared from lactic acid bacteria, lactobacillus acidophilus, bacillus subtilis, bacillus licheniformis, bacillus coagulans, aspergillus oryzae, bacillus megatherium, bacillus laterosporus, bacillus thuringiensis, streptococcus faecium, photosynthetic bacteria, saccharomycetes, paecilomyces lilacinus, nitrogen-fixing bacteria and actinomycetes. The facultative anaerobic fermentation fungicide can be suitable for facultative anaerobic fermentation of organic fertilizer, organic matter can be efficiently converted, and growth of pernicious bacteria can be inhibited. The invention also discloses a preparing method of the organic fertilizer, in the method, facultative anaerobic fermentation is carried out through the facultative anaerobic fermentation fungicide, the fermentation cycle is short, the running cost is low, the organic fertilizer prepared with the method is rich in nutriment, environmentally friendly and harmless, and development of ecological agriculture can be promoted.