The present invention relates to a preparation method of fingolimod intermediate, specifically relates to a preparation method of {5-[2-(4-n-octyl-phenyl)ethyl]-2,2-dimethyl-1,3-dioxane-5-yl} carbamic acid tert-butyl ester. The method includes performing cross-coupling reaction of a Grignard reagent prepared from n-octyl alkylogen with 4-halogen-benzoate, reducing the generated 4-n-octyl benzoate to 4-n-octyl benzyl alcohol, performing halogenation reaction to give 4-n-octyl benzyl halide, reacting the halide with triphenylphosphine to generate (4-n-octyl benzyl) triphenylphosphonium halide, performing Wittig reaction of the compound with (5-formyl-2,2-dimethyl-1,3-dioxane-5-yl) carbamic acid tert-butyl ester, generating {5-[2-(4-n-octyl-phenyl)-vinyl]-2,2-dimethyl-1,3-dioxane-5-yl}-carbamic acid tert-butyl ester, and preparing the compound by hydrogenation reduction.