A multichannel vertical vacuum transistor based on the Fowler-Nordheim tunneling emission mechanism was proposed and numerically investigated. The multichannel structure was demonstrated to be effective in enhancing the drain current when compared to the traditional single-channel structure with the same device size. For example, transconductance increased from 0.42 mS of the single-channel structure to 0.86 mS of the four-channel structure. In addition, when the vacuum channel number increases, the size of a single channel decreases correspondingly, leading to a reduction in electric field intensity on the electron emission surface. Thus, the off-state current dramatically reduced by two orders of magnitude reaching10(-15) A according to the simulated results. In other words, the ON/OFF drain current ratio of the multichannel structure is significantly enhanced. Furthermore, the simulation results indicate that the cut-off frequency of the multichannel device is 33% higher than that of the traditional single-channel one reaching 0.19 THz.