The invention relates to a preparation process of fatty acid isooctyl ester. The preparation process comprises the step of carrying out a reaction on fatty acid and isooctanol in the presence of a catalyst, wherein the catalyst is selected from acid sulfate, supported acid sulfate and supported p-toluenesulfonic acid as well as combination thereof. The process provided by the invention at least has one of the advantages of being high in reaction conversion rate, low in use level of isooctanol and catalyst, mild in reaction condition, free from or few in side reactions, simple in post-treatment process and environmentally friendly.