The invention discloses a catalyst for continuously preparing 3,5-dimethyl piperidine. The catalyst is prepared from an activated carbon carrier, Ru, Rh and M, wherein the Ru, the Rh and the M are loaded on the activated carbon carrier, the mass percent content of the Ru in the catalyst is 1% to 5%, the mass percent content of the Rh is 0.05% to 1%, the mass percent content of the M is 0.05% to 1.5%, and the M is Pt, K, Ce or Sn. In addition, the invention further discloses a preparation method of the catalyst and a method for continuously preparing the 3,5-dimethyl piperidine. The catalyst disclosed by the invention has the characteristics of high activity, high selectivity and high stability and can can realize high-efficient catalysis to prepare the 3,5-dimethyl piperidine in high efficiency; the converting rate of a raw material of 3,5-dimethyl pyridine is 100%, the yield of a product of the 3,5-dimethyl piperidine is larger than 99%, and cis-trans isomerism ratio is (87 : 13) to ( 83 : 17).