Abstract: The dispersion of nanoparticles in the scanning electron microscopy(SEM) test was studied by the commercial amorphous nanometric silica as research subject. An exhaustive research has been made under different physical and chemical conditions with different dispersing medium, the appropriate dispersion method was given at last and the application of nanoparticles in the scanning electron microscopy test is based on these. The research result shows that ethanol as dispersant or adding various surfactants can have dispersed effect, and ethanol as dispersant is makingthe significant difference. High resolution secondary electron images of synthetic nanometric silica were given in a practical application with the result.