The invention relates to a preparation method of 1, 2-aliphatic diol. The method consists of: under the condition of an organic solvent, taking the straight chain or branched chain terminal olefin of a carbon chain with a carbon atom number of 4-24 as the raw material, adding hydrogen peroxide and a catalyst, then performing stirring at 0-100DEG C for 1-6h, and conducting fractionation separation to obtain the product 1, 2-aliphatic diol. The catalyst is vanadium pentoxide or niobium pentoxide. The preparation method provided by the invention has the advantages of high yield, easy operation, and recyclability of the catalyst, etc.