Abstract: The electron beams produced by the needle-shaped annular carbon fiber-coated cathode soaked with cesium iodide (CsI) salt and annular stainless steel cathode were separately used to bombard the nylon targets. There was a uniform round mark on the target bombarded by the electron beam generated by the carbon fiber cathode, but there was a nonuniform mark on the target bombarded by the annular stainless steel cathode. It was believed that the different mechanism, characteristics and configuration between the carbon fiber cathode and the stainless steel cathode caused the difference of emission uniformity. Scanning with optics microscope, it was found that only the tips of the needle-shaped steel was destroyed. With electron microscope, it was found that both the tips and flanks of the carbon