The invention relates to the technical field of marine diesel engine tail gas post-treatment, in particular to an integral DOC catalyst for marine diesel engine tail gas purification and a preparation process thereof. The integral DOC catalyst for marine diesel engine tail gas purification takes cordierite honeycomb ceramic as the carrier, in terms of 100% of the mass of the cordierite honeycomb ceramic, the active components loaded on the cordierite honeycomb ceramic carrier includes: greater than or equal to 3%wt of palladium, and greater than or equal to 6%wt of the sum of cerium oxide and zirconium oxide. The DOC catalyst can well adapt to the special work conditions of marine diesel engine tail gas treatment, and also can effectively improve the problems of catalyst poisoning, catalytic carrier channel blockage, and high sulfate content of the tail gas.