The invention relates to a preparation method of 
cefoxitin. The method comprises the following steps: adding a 
solvent A into a compound 
aqueous solution with the structure shown in the formula (IV), adding N,N'-dibenzylethylenediamine diacetate or 
aqueous solution thereof, filtering to obtain a compound with an 
intermediate structure shown in the formula (III); adding the compound with the 
intermediate structure shown in the formula (III) into 
acetone or 
tetrahydrofuran, adding chloriosulfonyl 
isocyanate to react, and hydrolyzing; adding acetic 
ether, filtering, extracting, decoloring, 
salting out, and filtering to obtain a compound with an 
intermediate structure shown in the formula (II); adding the compound with the intermediate structure shown in the formula (II) into an 
organic solvent B, adding 
organic acid to dissolve, adding a 
methanol solution with 
sodium methoxide and tert-butyl 
hypochlorite to perform 
methylation reaction, adding 
sodium pyrosulfite and 
acetic acid for neutralizing, adding water for extracting, acidifying water phase, filtering to obtain 
cefoxitin. According to the preparation method, deacetyled 
cefoxitin always exists in a mode of 
sodium salt or amine salt, so that the condensation 
side reaction easily caused by low pH can be avoided, and the product quality and yield can be well controlled.