Abstract: With the further investigation on the periodontitis aetiology, the importance of the subgingival microbiological detection becomes more significant. The normal microflora is the ingredient and an obbliganto physiology system of the host. Oral microecology is a dynamic, oppositely and coherent. The balance of the oral microecology is a guarantee and the symbol of the body′s healthy. Once the balance is broken, dysbacteria will occur. The development of molecular biology technology provides rapid and effective technology and method on the
research of oral microbion. Denaturing gradient gel electrophoresis（DGGE） has the advantage of safety, reutilization, rapid and easy operation. It can be said that DGGE is a useful means of analysis on the change of the oral microecology.

Key words: periodontitis, denaturing gradient gel electrophoresis, subgingival microbial population, oral microecology