The invention provides a new method for preparing 1,2-pentadiol by using chloropentanol as a main raw material, which comprises the following steps: adding the chloropentanol and aqueous solution of an alkali into a reactor at room temperature; stirring the mixture, heating the mixture to 60 to 80 DEG C and keeping the temperature for reaction in a period till the reaction is completed; neutralizing the reactants with acid and/or distilling the reactants under normal pressure, and performing demixing to obtain 1,2-pentadiol; adding an organic solvent, a hydration catalyst and water, stirring the mixture, heating the temperature to 30 to 100 DEG C, keeping the temperature for reaction in a period till the reaction is completed, neutralizing a water layer with an alkali if the water layer is acidic, dehydrating under a reduced pressure to obtain a coarse product of the 1,2-pentadiol, and distilling to obtain high-purity 1,2-pentadiol. The invention has the advantages that: the process flow is simple; the reaction conditions are mild; the yield is high; and the purity of the prepared 1,2-pentadiol is higher than 99.9 percent.