The invention discloses a method for synthesizing and preparing 5'-S-(4, 4'-dimethoxytriphenylmethyl)-2'-deoxyinosine. The method comprises the following steps of: under inert gas protection, carrying out mitsunobu reaction on 2'-deoxyinosine and 4, 4'-dimethoxytriphenylmethyl mercaptan in an organic solvent at room temperature under effects of an azo reagent, a phosphine coordination compound, organic alkali or protonic acid, i.e. carrying out intermolecular dehydration reaction on 5'-hydroxyl of the 2'-deoxyinosine and the 4, 4'-dimethoxytriphenylmethyl mercaptan to obtain a C-S bond, and obtaining the 5'-S-(4, 4'-dimethoxytriphenylmethyl)-2'-deoxyinosine. The method for synthesizing and preparing the 5'-S-(4, 4'-dimethoxytriphenylmethyl)-2'-deoxyinosine has the beneficial effects of being wide in raw material sources, low in price, high in yield, mild in reaction condition, good in selectivity, simple in operation process, convenient in post-treatment, and suitable for large-scale industrial production.