The invention belongs to the technical field of fine chemical engineering, and relates to a method for continuously preparing N, N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, and the method helps to realize continuous and low-pressure production of N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, so that cost is saved and economical benefit is raised. The method comprises: mixing p-phenylenediamine (or p-nitroaniline ) and 5-methyl-2-hexanone according to a certain ratio, continuously conveying to a preheater, keeping the preheater at 110-150 DEG C, then enabling preheated materials to enter into a narrow and long reactor loaded with a solid catalyst via a pipeline, and keeping the reactor at 150-200 DEG C, at the same time continuously introducing hydrogen with a pressure of 0.5-2.5 MPa into the reactor, after the materials are reacted, collecting the product into a gas-liquid separator via a cooler, moving out the reaction solution and performing reduced pressure distillation to obtain N, N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. The conversion rate of p-nitroaniline is 99% or more and selectivity is 95% or more.