In this paper, the authors bring forward a novel method named as the field-inducing self-assembly process in which free-standing MWCNTs array can be assembled perpendicularly on silicon (111) wafer. The density of free-standing MWCNTs array is controllable by adjusting the DC voltage from 0 V to 40 V. Preferential MWCNTs array is obtained by the condensation reaction between carboxylic group of MWCNTs end and hydroxyl group of silicon electrode surface under a low DC field. And the MWCNTs array can exhibit excellent field emission property.