Theoretical and experimental results of intense beam confinement by conducting meshes in a relativistic klystron amplifier (RKA) are presented.Electron motions in a steady intense electron beam confined by conducting meshes are analyzed with an approximate space charge field distribution. And the conditions for steady beam transportation are discussed.Experimental results of a long distance (60cm) transportation of an intense beam (400kV,2.5kA) generated by a linear induction accelerator are presented.Experimental results of modulated beam transportation confined by the mesh array are presented also.The results show that the focusing ability of the conducting meshes is not very sensitive to the beam energy.And the meshes can be used effectively in a RKA to replace the magnetic field system.