The invention provides a preparation method of a
formamide phenazine bio-
fungicide. The preparation method comprises the following steps: firstly, implementing shake-flask culture on activated
pseudomonas chlororaphis and
pseudomonas aeruginosa, so as to obtain a seed solution A and a seed solution B; inoculating a
fermentation medium with the seed solution A, conducting
fermentation culture for 20h, inoculating the
fermentation medium with the seed solution B, simultaneously refilling a
nutrient solution, and continuing to implement fermentation culture for 40-50h, so that fermentation brothis obtained; centrifuging the
fermentation broth at high speed, regulating pH value, and conducting extracting and concentrating, so as to a crude product; and implementing
column chromatography and separating, so that the
formamide phenazine bio-
fungicide is obtained. The culture medium and culture conditions provided by the invention are quite suitable for growth of strains; the refilled
nutrient solution contains
chorismic acid; two strains undergo mixed fermentation; the content of
formamide phenazine in the
fermentation broth is obviously improved; based upon a series of post-treatment, afinished product that purity is higher than 99% is separated and obtained; and the finished product takes a strong
inhibitory effect on pathogenic fungi of plants.