Abstract: The paper introduced micro-emulsion composited filter-aids and its constituent elements,tested its effect of filter-aid,and studied its adsorption quantity and ξ-level on surface of coal,also made the infra-red spectroscope analysis on it.The result shows that the effect of the composited filter-aids is not the simply plus of effect of each composition in this filter-aids,each composition not only gives its own effect,but also in coordination with each other gives the comprehensive effect of dewatering,therefore,this filter-aids is both reduced the water content of cake and increased the filtration velocity.