The invention discloses a cobalt-based catalyst as well as a preparation method and application thereof to synthesis of 3-hydroxycarboxylate. The cobalt-based catalyst comprises: nano metal cobalt which is used as a main active component, a porous material which is used as a composite carrier, and a nitrogen-doped carbon material, wherein the nano metal cobalt is uniformly loaded on the porous material; the surface of the nano metal cobalt is coated with the nitrogen-doped carbon material. The preparation method comprises the following steps: enabling a mixed reaction system containing a cobalt source, a carbon-nitrogen precursor and a solvent to react at 25 to 80 DEG C for 0.5 to 2h, and adding the porous material; then roasting at 550 to 900 DEG C for 2 to 3h in a protective atmosphere to obtain the cobalt-based catalyst. The cobalt-based catalyst provided by the invention has stable structure and properties and high reaction activity and 3-hydroxycarboxylate selectivity; the cobalt-based catalyst has the advantages that the preparation method is simple, the catalyst is easy to separate and recycle after reaction, the catalytic property of the catalyst is not reduced after the catalyst is repeatedly used for a plurality of times and the like, so that the catalyst is more suitable for industrial amplified application.