The invention relates to a preparation method of a high-thermal-conductivity carbon/carbon-copper composite material. A metal copper element is introduced into a carbon/carbon composite material by utilizing an aqueous solution of inorganic metal copper salt and adopting a soaking-heating-drying-pyrolysis-in-situ carbon thermal reduction reaction method. A densified carbon/carbon composite material sample with the density of 0.4-1.2 g/cm<3> is cleaned for standby application; a certain amount of inorganic metal copper salt saturated solution is prepared, the sample is soaked in the salt solution and is subjected to heating and ultrasonic treatment; the sample soaked by using the inorganic saturated salt solution is subjected to dying and high-temperature heat treatment to obtain a carbon/carbon composite material with required metal copper content; finally, the sample is subjected to final densification to obtain the high-thermal-conductivity carbon/carbon-copper composite material. The preparation method of the carbon/carbon-copper composite material has low device requirements, and the metal copper element can be introduced into the prepared material as required and can be uniformly distributed in the material. The prepared carbon/carbon-copper composite material has excellent heat-conducting and mechanical properties.