This paper developed a new clean continuous process for the hydrogenation of 3,5-dimethylpyridine (DPY) to 3,5-dimethylpiperidine (DPI) without solvent. A series of Ru/C catalysts were prepared by impregnation method, which were characterized by the BET, ICP, CO chemisorptions, XRD, SEM, EDS, TEM and TG. The effect of active species, loading, catalyst support, reaction temperature and pressure on the catalytic performance was investigated. The influence of internal and external diffusion in the trickle-bed reactor (TBR) was basically eliminated by adjusting the particle size and dosage of the Ru/C catalyst. The reaction performance of the hydrogenation of DPY to DPI in the TBR and kettle reactor (KR) was compared, and the superiority of the TBR process was analyzed. The results show that this new continuous process developed in this study is an efficient way to realize the hydrogenation of DPY to DPI, and has a good industrial application prospect.