NOVELTY - A mesoporous carbon/graphite flake composite material is prepared by subjecting expanded graphite to thermal expansion treatment, adding treated materials to a surface active agent A solution, heating while stirring, and vacuum drying; mixing surface active agent B and solvent B, adding hydroxy derivative and aldehyde, and heating while stirring to obtain mesoporous carbon precursor solution; adding dropwise obtained precursor solution to the vacuum dried product, vacuumizing, and subjecting to microwave treatment; and heating, and carbonizing in the presence of inert gas.    USE - Method of preparing a mesoporous carbon/graphite flake composite material for fuel cell, lithium ion battery or supercapacitor.    ADVANTAGE - The method is simple and low cost, utilizes cheap raw materials, can be applied to industrial production, and prepares product having good electrical conductivity, controlled thickness, controlled hole diameter and big specific surface area.    DETAILED DESCRIPTION - A mesoporous carbon/graphite flake composite material is prepared by:    (A) subjecting expanded graphite to thermal expansion treatment, adding treated materials to a surface active agent A solution at a mass ratio of 1-10:10, heating while stirring, and vacuum drying;    (B) mixing surface active agent B and solvent B at a mass ratio of 1:20-50, adding hydroxy derivative and aldehyde having a mass ratio of 1:3-6, and heating at 50-75 degrees C for 30 minutes to 29 hours while stirring at a speed of 200-400 revolutions/minute (rpm) to obtain mesoporous carbon precursor solution;    (C) adding dropwise obtained precursor solution to the vacuum dried product at a ratio of 50-300:1, vacuumizing for 5 minutes to 2 hours, and subjecting to hydrothermal or microwave treatment; and    (D) heating at 600-1000 degrees C with a temperature gradient of 2-20 degrees C/minute, and carbonizing at room temperature for 6 hours in the presence of inert gas controlled at a flow rate of 120-400 ml/minute.    The surface active agent A solution comprises surface active agent A and organic solvent having a mass ratio of 1:10-500. The solvent is water, ethanol, propyl alcohol and/or glycose. The solvent B is water and/or ethanol. The weight ratio of hydroxy derivative and solvent B is 1:8-20.