Droplets produced by continuous-ink-jet printing are widely used in various fields. The gas pressure in the feedstock tank and the perturbation imposed on a capillary jet are the primary parameters to control the formation process of the droplets. However, the lack of a simple method for producing perturbation is a major limitation of continuous-ink-jet technology. Therefore, based on the technology of electromagnetic force perturbation, a novel and simple system to produce the desired perturbation frequency is constructed in this article. Experiments were conducted with distilled water. The droplet formation process experiences three modes with the increase of the disturbance frequency. The uniform droplets could be produced in a certain region when the gas pressure in the feedstock tank is constant, and the variation of the jet tip had an important influence on the uniform droplet formation. The size of droplets could be changed by the control of the disturbance frequency.