The invention discloses a plastic master batch, and a preparation method and application thereof. The plastic master batch comprises a polymer matrix, graphene, a filling material, a coating agent, adispersant, an antioxidant, a crosslinking agent and an assistant crosslinking agent. Therefore, the plastic master batch has the characteristics of high thermal conductivity, high oxygen resistance,easiness in welding and uniform dispersion of graphene; and therefore, a capillary network prepared from the plastic master batch has the advantages of high thermal conductivity, high oxygen resistance and easiness in welding, so that cold and heat in a system are quickly transferred to the outside, efficient circulation of a medium is realized, energy waste is avoided, and popularization and application of a capillary network air conditioning system are facilitated.