In pharmacology, development of a formulated nanosuspension, a potential drug delivery system for poorly soluble drugs, has been investigated to overcome the bioavailability problems caused by weak solubility, limited chemical stability following administration (i.e., a short half-life), poor bioavailability, and potentially strong side effects requiring drug enrichment at the site of action. For first time use in a pesticide delivery system, a two-step milling process for preparing a nanosuspension in a system of active compound/surfactant/water is described in this paper. First, all the components were mixed at a certain composition to prepare a microsuspension by the general milling process. Then, the microsuspension was taken into a nanomilling process with zirconium oxide beads, having a diameter range of 0.1-0.2 mm, as the milling media to generate the nanosuspension. Therefore, a nanosuspension concentrate was formed. To demonstrate the potential applications of this novel system, it was used to make a formulation with a poorly soluble crystalline insecticide, carbofuran. In a comparative study, two kinds of carbofuran formulations, a microsuspension (commercial) and a nanosuspension, were administered to a diamondback moth (DBM) to test their efficacy and stability as a pesticide. The results indicate that carbofuran has the same efficacy at a lower dose for the nanosuspension compared to the microsuspension. The nanosuspension system was also physically and chemically stable over a period of 2 years, as indicated by the unchanged particle size and specification tests.