The invention relates to a substitute material for rehabilitating articular cartilage and a preparation method thereof. A substitute material body is a porous hydrogel structural body with an interpenetrating network structure polymerized by PVA and PVP type components; the mass ratio of polyvinyl alcohol to pyrrolidone type components is 1: (0.01 to 1); and the elastic modulus is 0.5 to 10 MPa. The substitute material is prepared by adopting an in-situ solution polymerization method and the preparation method comprises the following steps: dissolving the monomers of the PVP type components in PVA solution and mixing completely and uniformly; adding a free radical initiator and polymerizing to obtain a blending system of the PVP type components; then adding a cross-linking agent to continuously carry out cross-linking polymerization reaction to obtain a hydrogel product; and finally preparing the substitute material through repeatedly freezing/unfreezing till the hardness reach the expected index. The substitute material is of a porous structure with an interpenetrating network which can contain a large amount of water and is a permeable material; liquid can be permeated and extruded as a lubricant under the load action; and furthermore, the substitute material has good mechanical strength approximate to the mechanical property of the articular cartilage, is similar to naturalcartilage tissues, and has good biological compatibility.