Scanning Electron Microscope and Energy Dispersive Analysis (SEMEDS) were used to study the elements of particles in drinking water treatment effluents, to conduct the distribution characteristics of particles and distribution probability of main elements, and to analyse the possible structure of individual element in the Granular Activated Carbon(GAC) effluents particles. It was indicated that there were more elements in particles at GAC inlet and outlet, in which the major elements were Ca、Fe、Al 、Si 、C、O. And the concentration of nonmetal elements was absolutely higher than that of metal elements. The shapes of particles were various, in which most of them were irregular and very few were baculiform, spherical or flocculent. The molar ratio of (C+O) to (Ca+Fe+Al+Mg) in particles had a wide range, from 1.0 to 40, in eight samples, in which ratios of two samples were 1.0-3.0 and five were over 7.0.