Abstract: Coagulation behavior in different pH conditions was studied in composite emulsion systems containing styrene acrylate resin, wax and pigment components. The content of each component and the micro structure in the coagulated particles were analyzed by elemental anyalyzer, differential scanning calorimetry (DSC), optical micrography(OM) and electron microscopy(EM). Results showed that the coagualtion efficiency of each component in the composite state was much higher than that in separating state. The wax emulsion itself was the most stable among the three components and no coagulation was observed in the whole pH range. However, its efficiency in the composite system was found to be even higher than the less stable styrene acrylate resin emulsion. Transmission electron microscopy(TEM) observation demonstrated that the synergistic coagulating effect could be ascribed to the encapsulating of the positively charged pigment particles on the large size negatively charged wax particles, leading to the high coagulation efficiency in the composite system.