The invention discloses a preparation method of a 1,2-diaminopropane o-vanillin double-Schiff base corrosion inhibitor. The method includes the steps of firstly, weighing 1.1411g of o-vanillin, placing into a round-bottom flask containing 15mL of anhydrous ethanol, and evenly stirring through magnetic stirring; secondly, adding 0.1853g of analytically pure 1,2-diaminopropane and 0.15mL of glacialacetic acid, stirring at 65 DEG C, and performing reflux reaction under nitrogen protection for 6 hours; thirdly, cooling under room temperature, performing reduced pressure suction filtration, constantly eluting with anhydrous ethanol, taking out filter cake, and performing vacuum drying on the filter cake; fourthly, placing the filter cake into a beaker containing 40mL of anhydrous ethanol, stirring, performing reduced pressure suction filtration, taking the filter cake, and performing vacuum drying to obtain the 1,2-diaminopropane o-vanillin double-Schiff base corrosion inhibitor applicableto the corrosion prevention of carbon steel in a pickling solution. The method is simple in process, good in repeatability and high in yield, and the prepared corrosion inhibitor is good in corrosioninhibition effect on the carbon steel in dilute sulfuric acid.