A natural functional compound, i.e., fragrant oil, has been studied in the microencapsulation field. Urea-formaldehyde ws used as the prepolymer for the skin layer in microencapsulation. The microcapsules containing the natural functional compound were produced by in situ polymerization with the prepolymer. Analysis of the shape and particle distribution of microcapsules were carried out using and image analyzer. The diameters and distribution ranges of the microcapsules were controlled by different factors, such as, stirring time, emulsifier, and viscosity. The average diameter of microcapsules decreased with increase in both the stirring rate and stirring time. In the presence of the emulsifier, the average diameter decreased up to 5g emulsifier in 100$mell$ deionized water, and then increased as the emulsifier concentration increased, resulting from the variance of viscosity. The dependence of average size on viscosity was discussed in the reunification of natural functional compound in a core system.