The invention relates to a method of using 2,5-hexanedione for synthesizing liquid cycloalkanes. 2,5-hexanedione serves as a raw material, and under the effect of a static-bed continuous reactor firstbed layer catalyst, through aldol condensation and hydrogenation reaction, oxygen containing organic compounds with the carbon numbers of 6, 12 and 18 are obtained; under the effect of a static-bed continuous reactor second bed layer catalyst, the oxygen containing organic compounds are further subjected to hydrodeoxygenation reaction to prepare target liquid cycloalkane products with the carbonnumbers of 6, 12 and 18. The method is simple in process route and environmentally friendly, and a new effective approach for using 2,5-hexanedione for preparing liquid cycloalkanes is provided.