In this paper, four typical types of high purity graphite and their titanium carbide coating modified materials were tested as anodes in high current electron beam diodes. The results show that the currents of the diodes were obviously different when the graphite anodes were under electron beam bombardment with voltage 860 kV, current 11 kA and pulse width 40 ns. The current curve for graphite 4# was normal even after interaction of 167 electron pulses while the other graphite current curves showed different degrees of tail erosion. The ablative experiments of titanium carbide coating on graphite further verified the difference of the graphite, indicating that the thermal conductivity of graphite has an important effect on its ablative resistance. The higher the thermal conductivity of graphite, the lower the degree of recrystallization of titanium carbide, the better the corrosion resistance of graphite. Therefore, graphite 4# has an excellent resistance to electron beam bombardment and would be promising for application as collector materials in relativistic traveling wave tubes.