The invention provides a preparation method of
milbemycin oxime. The preparation method of
milbemycin oxime comprises the following steps: extracting milbemycins, namely taking milbe mycelia obtained through
fermentation as a
raw material, extracting, concentrating, extracting, concentrating, extracting again and concentrating again, so as to obtain
milbemycin; preparing milbemycin
ketone, namely taking the milbemycin as a
raw material, establishing an oxidation
reaction system, after reaction is finished, filtering, concentrating, extracting and concentrating the
reaction system, so as to obtain an
intermediate product milbemycin
ketone; synthesizing
milbemycin oxime, namely dissolving milbemycin
ketone with
methanol and dioxane, dropwise adding
hydroxylamine hydrochloride solution and reacting, concentrating the
reaction system, extracting,
drying and concentrating, so as to obtain a
milbemycin oxime crude product; and purifying
milbemycin oxime, namely crystallizing the milbemycin
oxime crude product with a mixed
solvent of trichloromethane and normal
heptane, dissolving a crystalline product with
ethanol, dropwise adding into water while stirring for carrying out
crystallization, filtering, and
drying, so that the milbemycin oxime finished product is obtained. The preparation method of the milbemycin oxime has the advantages that productivity is greatly improved, and cost is obviously reduced, so that the preparation method provided by the invention is obviously better than an existing preparation method.