The invention discloses a method for preparing 1, 2-pentanediol from n-butanol as a raw material. The method comprises that 1) n-butanol as a raw material undergoes a catalytic oxidation reaction to produce n-butyraldehyde, 2) a ylide reagent is added into the n-butyraldehyde under alkaline conditions and the mixture undergoes a ylide reaction to produce 1, 2-cyclopentene oxide, and 3) the 1, 2-cyclopentene oxide is hydrolyzed into a desired product 1, 2-pentanediol. Compared with the prior art, the method utilizes cheap and easily available n-butanol having a sufficient source as a raw material, simplifies the process for synthesizing and separating to purify 1, 2-pentanediol, improves the reaction conversion rate and the purity of the product and greatly reduces reaction time and cost. Compared with the process using n-pentene as a raw material, the method greatly reduces a production cost, can be carried out under mild and reliable production conditions, is stable and safe and solves the problem that the existing device is easily corroded by a strong acid and formaldehyde pollutes the environment.