The invention relates to a method for biologically modifying a p-phenylenediamine anti-aging agent catalyst, wherein 4-aminodiphenylamine and fatty ketone are used as raw materials, a biological modifier is added according to a certain ratio, and condensation hydrogenation is performed in a tower reactor or high-pressure kettle by using a catalyst to produce the corresponding p-phenylenediamine anti-aging agent. According to the invention, the modification is not required to be carried out at the catalyst preparation stage, and can be performed by adding the biological modifier into the reaction liquid according to a certain ratio so as to effectively improve the conversion rate and the selectivity of the catalyst, reduce the ketone-to-alcohol side reaction and reduce the production wasteliquid, such that the ketone-to-alcohol side reaction cannot be generated under the optimized process conditions; and the results of the embodiments and the control show that the good effect is achieved by adding the biological modifier, and particularly the implementation effect of the fixed bed reactor is superior to the implementation effect of the high-pressure kettle in the inhibiting of ketone-to-alcohol side reactions.