The invention relates to a one-pot method for preparing phenyl heptadecane. The method comprises the step: with oleic acid and benzene as raw materials, by using the characteristics that a support bifunctional catalyst has the catalytic function of catalyzing oleic acid and benzene to perform an alkylation reaction and catalyzing phenyl octadecanoic acid to perform a decarboxylic reaction, developing the one-pot method for preparing the phenyl heptadecane from oleic acid and benzene. The method is simple and convenient in operation, and beneficial for industrial production. Through the technology, the conversion rate of oleic acid reaches more than 99%, the selectivity of phenyl heptadecane reaches up to more than 97%, and the purity of the product reaches more than 98.5%.