The formation mechanism of Spindt-type metal emitter is investigated by the simulation and the fabrication. There are several factors in this mechanism. The aspect ratio (emitter height/bottom diameter of emitter) is the major factor determined mainly by the physical properties of evaporation materials and process conditions. On the emitter tip, the emission current depends on the aspect ratio that affects the suitable current density for field emission display. In the fabrication of metal emitter by electron beam evaporator, the dependence of the aspect ratio on materials and process conditions is analyzed by the particle simulation using the modified ballistic deposition model. From these results, the formation mechanism of the metal field emitter is analyzed with experimental data, therefore the optimized process condition is obtained for a suitable aspect ratio.