The invention relates to a method for preparing tert-butyl acetate, and in particular relates to a method for preparing tert-butyl acetate based on acetic acid and isobutene-containing C4 as raw materials. The method is characterized by adding a polymerization inhibitor in a reaction process, wherein the polymerization inhibitor is a component A or a component B or a mixture of the components A and B, wherein the component A is selected from phenols, diphenols, benzoquinone and derivatives thereof or phenothiazine compounds, and the component B is a hydroxylamine compound or piperidine derivative. By adopting the method provided by the invention, the self-polymerization reaction of isobutene can be well inhibited, the selectivity of tert-butyl acetate is greatly improved, and separation process is simplified.