The invention provides a preparation method of 
sodium avibactam. The method comprises that 
sodium 2-ethylhexanoate reacts with an intermediate 
compound K, so that the 
sodium avibactam is obtained. Theinvention also provides a preparation method of the intermediate 
compound K. The preparation method comprises the following steps: (1) carrying out reaction on a compound J with 
ammonium formate, 
formic acid and 
triethylamine in presence of a catalyst, and removing benzyl, so that a 
compound K1 is obtained; (2) adding an acid binding agent, a sulfonation 
reagent and water into the K1 reaction liquid obtained in the step (1), and reacting; and (3) adding tetrabutylammonium acetate 
aqueous solution into the reaction liquid obtained in the step (2), stirring and reacting, then adding an extraction 
solvent, separating out an organic phase, 
drying, then distilling off the 
solvent, adding a 
crystallization solvent, stirring, and crystallizing, so that the compound K is obtained. The preparationmethods provided by the invention are low in cost, avoid a high-risk preparation method for debenzylation through hydrogenation, are high in safety performance, easy to operate and applicable to industrial production and have greater application value.