Effects of the structure and morphology of kaolinites on hydrazine intercalation rate were investigated. It was found that the intercalation rate and the intercalating yield for the tubulose morpho logy Suzhou kaolinite is less than that for the platelike Maoming kaolinite which have more open structure. There exist definite high and low concentration thresholds of hydrazine solution in effective intercalation for Suzhou clay, differing from Maoming clay which has only a low hydrazine concentration limit. However, they have same optimum hydrazine concentration for the highest intercalation rate. The clay with smaller particle size is found more difficult to be intercalated. This phenomenon, discrepant with common sense, is interpreted by the increasing crystal perfection of clay with larger particles. Therefore, the ease of hydrazine intercalation into kaolinite must be measured comprehensively by the structural openness, the weakness of bonding force between layers and the crystal perfection of kaolinite.