The invention discloses a carbendazim preparation method. Being improved based on a traditional synthesis technology, the carbendazim preparation method is characterized in that firstly, a methylbenzene and water biphasic solvent reaction system is adopted, so that carbendazim appearance is improved, carbendazim is bright white, purity can be above 99.8% and carbendazim grade is increased; secondly, a method that concentrated hydrochloric acid and a methyl cyanocarbamate cyclizing agent are added dropwise simultaneously is adopted, and carbendazim yield can be above 97.5%. Compared with an existing traditional synthesis technology, the carbendazim preparation method has the greatest advantages that carbendazim yield is high, and the carbendazim is excellent in color and luster and high in purity, thereby being a method capable of preparing the high-quality carbendazim.