The invention belongs to the technical field of intermediate synthesis in fine chemical engineering, and particularly relates to a novel industrialized synthesis technique for preparing cinnamic acid from cinnamic aldehyde by catalytic oxidation. The technique comprises the following steps: (A) adding sodium hydroxide, pure water and catalyst mixed solution in a mass ratio of (8-40):180:(1.1-2.2) into a reaction kettle, stirring, introducing pure oxygen, dropwisely adding cinnamic aldehyde into the mixed solution at proper rate to generate sodium cinnamate, and standing for 10-40 minutes to deposit the catalyst; and (B) leading out the sodium cinnamate solution obtained in the step (A), carrying out acid precipitation at 70-80 DEG C, keeping the reaction for 15-40 minutes, and naturally cooling to room temperature, thereby obtaining the cinnamic acid. The catalyst is nano silver particles. By adopting the supporter-free nano silver particles as the catalyst for the first time, the invention solves the problems of catalyst poisoning, high shedding tendency, high loss and the like, simplifies the production technique, greatly lowers the production cost, has the advantage of high yield, and implements industrialized mass production.