The invention relates to a plastic crystal polymer electrolyte material prepared by in-situ polymerization and a preparation method therefor, and belongs to the technical field of an electrolyte material. The plastic crystal polymer electrolyte material prepared by the in-situ polymerization comprises a monomer, an initiator, a cross-linking agent, a lithium salt, and plastic crystals; a mixed solution of the monomer, the initiator, the cross-linking agent, the lithium salt and the plastic crystals is heated to be subjected to the in-situ polymerization to obtain the plastic crystal polymer electrolyte material; the preparation method for the plastic crystal polymer electrolyte material prepared by the in-situ polymerization comprises the steps of mixing and dissolving the monomer, the initiator, the cross-linking agent, the lithium salt and the plastic crystals; and pouring the solution into a polytetrafluoroethylene die, and heating and performing the in-situ polymerization to obtain the plastic crystal polymer electrolyte material. By adoption of a one-step method for synthesis, the preparation process is simple and industrial production can be realized favorably; and in addition, the plastic crystal polymer electrolyte material is high in conductivity at room temperature, high in thermal stability and interface stability, high in mechanical property, excellent in electrochemical performance, and the like.