Abstract: 【Objective】The purpose of this experiment is evaluate the effects of combined use of anionic and nonionic surfactants on the formation and stability of beta-cypermethrion microemulsification. 【Method】The phase behavior and the maximum solubilization capacity of different mixed oil-mixed surfactants-water systems were studied in a pseudo-ternary phase diagram. 【Result】The results indicated that the isotropic and monophasic area could be diluted with water to nearly 100% area in the phase diagrams and the solubilization capacity of surfactants mixtures increased significantly as the anioic surfactant Nongru 500# and the nonionic surfactant Nongru 400# were composed at the mass radio of 1:1, 1:2 and 1:3. Compared with Nongru 400#, the concentration of combined use of Nongru 500# and Nongru 400# at a suitable mass radio of 1:2 used for the microemulsification to the same phase volume of beta-cypermethrion and oil decreased to 11.5% from 52.5%. 【Conclusion】It seems that the combination of nonionic surfactant and anioic surfactant at a suitable mass radio is beneficial to the decrease of surfactants dosage and the increase of pesticide active ingredient in the pesticide microemulsion and it will improve the quality of beta-cypermethrion microemulsion and make it more competitive in the market.

Key words: Pesticide microemulsion, pseudo-ternary phase diagram, phase behavior, maximum solubilization capacity, beta-cypermethrion