The invention belongs to the field of pharmaceutical chemicals, and relates to a preparation method of an antimicrobial compound, specifically to a preparation method of tedizolid phosphate. In the preparation method, an intermediate in each step and the final product are high in purity. Further, diisopropylamino dibenzyl phosphite is taken as a phosphorylation reagent to avoid generation of dimerized products, and therefore the preparation method is high in yield. The preparation method is short in route and mild in reaction condition and is green and eco-friendly, and highly toxic reagents are avoided. Ultralow-temperature reactions are avoided, and the preparation method is simple and easy to operate and high in production efficiency. Thus, the preparation method is particularly suitable for industrial production.