Abstract: Emulsion stability is one of the technical parameters for stable quality of microemulsions. The influence of organic solvents, surfactants and the contents of active ingredient on the emulsion stability of the microemulsion were studied. In order to explorer the mechanism of emulsion stability at the microcosmic level, the hydromechanical radius of the disperse phase on microemulsion and its distribution were tested by means of the light scattering. The results showed that admixture of some organic solvents would be the optimal choice for elimination of the microemulsion instability. Emulsion stability is closely related to hydromechanical radius within the radius of microemulsion. It is necessary to adjust the balance of hydrophilicity and lipophilicity of the added surfactants in the system, as well as to restrict the contents of active ingredients in order to obtain the emulsion stability.