The invention discloses a cyclohexanone oxime synthesis method. In the process of preparing a flue gas desulfurization byproduct cyclohexanone oxime, sulfur dioxide in flue gas is absorbed by utilizing ammonia or ammonia water as an absorbent to prepare ammonium bisulfite, and the ammonium bisulfite serving as a raw material reacts with cyclohexanone by means of counter-current oximation to prepare cyclohexanone oxime. According to the method, by increasing the concentration of hydroxylamine sulfate and adding the organic solvent, the diffusion performance of a reaction system is improved and consumption of cyclohexanone is reduced; furthermore, due to the extraction effect of the organic solvent, the total content of cyclohexanone-oxime and cyclohexanone in the inorganic phase which leaves a cyclohexanone oxime synthesis system can be reduced to lower than 0.30wt%, and the yield of the cyclohexanone oxime synthesis reaction is increased.