The invention relates to a cathode catalyst for use in electrochemical reduction conversion of carbon dioxide. The cathode catalyst comprises a first catalyst layer and a second catalyst layer, wherein the second catalyst layer is formed on the surface of the first catalyst layer, and is of a porous structure; the first catalyst layer and the second catalyst layer are physically bonded with each other, and are made of different materials. The invention further relates to a cathode material for use in electrochemical reduction conversion of carbon dioxide. The cathode material comprises the cathode catalyst. The invention further relates to a reactor for use in electrochemical reduction conversion of carbon dioxide. The reactor comprises the cathode material. The invention further provides a preparation method of the cathode material.