Many scholars have made contributions on the formulae of the colloidal dispersion gel (CDG) and the factors affecting on the gelation performance．However

few reports were concentrated on studying the microstructure of the CDG．Polyacrylamide(HPAM)／ Chromium acetate and HPAM／phenolic aldehyde colloidal dispersion gel

which come respectively from different cross-linking systems

inorganic and organic

were studied by the microscopic image analysis with the atomic force microscope(AFM)．All of the CDG is founded to present eventually a self-assembly branch-like fractal structure under the scanning range of micrometer magnitude

and the fractal of a single twig was formed by compact stock of nanometer particles on a smaller scale regardless of the concentration variation of HPAM and the cross-linking reagent in either inorganic cross-linking system or organic cross-linking system．It is revealed that formation and morphology of the branch-like fractal structure depend on the concentration of HPAM

and the presence and concentration of cross-linking reagent only affect the topography of branch-like gel fractal．Moreover

the experimental results demonstrate that the elastic modulus of the gel with the fractal structure formed by the nanometer colloid particles is higher one order of magnitude than that by micrometer ones

and that the smaller the particle diameter is

the higher the gel kinetic stability is．