Abstract: The polycarboxylate and polyoxyethylene ether phosphate composite system is beneficial to improve the physical stability of pesticide aqueous suspensions. In this study, tebuconazole 430 g/L suspension concentrate (SC) was selected as the research object. The micelle hydrodynamic diameter of the polycarboxylate dispersant 850 and the polyoxyethylene ether phosphate dispersant 601p composite system and their effects on the viscosity, zeta potential, specific absorbance and rheological properties of tebuconazole were studied in detail. The results showed that the dispersion stability of tebuconazole SC prepared using 601p alone was higher than that using 850. And the stabilities of tebuconazole SC prepared by the above mentioned two composite systems were significantly higher than that of the single dispersant. Further studies demonstrated that the proportion of dispersant system also had influence on the physical stability of tebuconazole SC. When m(850) : m(601p) = 1 : 1, the micelle dynamic diameter of the composite dispersant is stable, and the prepared tebuconazole SC has the best dispersion stability. Specifically it exhibited a relatively small viscosity, and the zeta potential is –40.8 mV.