Abstract: Drilling fluid is the first extraneous fluid which contacts the hydrocarbon reservoir and often invades the reservoir more or less under a certain pressure difference. If drilling fluid filtrate is not compatible with the reservoir, it is very possible to cause the clay hydration expansion, water blocking, emulsification and chemical flocculation sedimentation, and then result in reservoir damage. Through the research on treating agent to the clay particle electric properties and the hydrated characteristic influence, the relationship between clay particle electric properties and the hydrated suppression has been analyzed. The results provide guidance for optimal drilling fluid treating agent, optimized drilling fluid formula, the analysis of treating agent action mechanism and are good for establishing the new suppression assessment method.